diff --git a/lang/en/search.php b/lang/en/search.php
index 6eba816562137..ea1327149637c 100644
--- a/lang/en/search.php
+++ b/lang/en/search.php
@@ -26,6 +26,7 @@
 $string['all'] = 'All';
 $string['allareas'] = 'All areas';
 $string['allcourses'] = 'All courses';
+$string['allusers'] = 'All users';
 $string['author'] = 'Author';
 $string['authorname'] = 'Author name';
 $string['back'] = 'Back';
diff --git a/lib/amd/build/form-autocomplete.min.js b/lib/amd/build/form-autocomplete.min.js
index e5c8906dcd484..954829bfdd07a 100644
--- a/lib/amd/build/form-autocomplete.min.js
+++ b/lib/amd/build/form-autocomplete.min.js
@@ -1 +1 @@
-define(["jquery","core/log","core/str","core/templates","core/notification"],function(a,b,c,d,e){var f={DOWN:40,ENTER:13,SPACE:32,ESCAPE:27,COMMA:44,UP:38},g=a.now(),h=function(b,c){var d=a(document.getElementById(c.selectionId)),e=d.children("[aria-selected=true]").length;for(b%=e;b<0;)b+=e;var f=a(d.children("[aria-selected=true]").get(b)),g=c.selectionId+"-"+b;d.children().attr("data-active-selection",!1).attr("id",""),f.attr("data-active-selection",!0).attr("id",g),d.attr("aria-activedescendant",g)},i=function(b,c,f){var g=[],i=a(document.getElementById(c.selectionId)),j=i.attr("aria-activedescendant"),k=!1;j&&(k=a(document.getElementById(j)).attr("data-value")),f.children("option").each(function(b,c){a(c).prop("selected")&&g.push({label:a(c).html(),value:a(c).attr("value")})});var l=a.extend({items:g},b,c);d.render("core/form_autocomplete_selection",l).done(function(b){i.empty().append(a(b).html()),k!==!1&&i.children("[aria-selected=true]").each(function(b,d){a(d).attr("data-value")===k&&h(b,c)})}).fail(e.exception)},j=function(a){"undefined"!=typeof M.core_formchangechecker&&M.core_formchangechecker.set_form_changed(),a.change()},k=function(b,c,d,e){var f=a(d).attr("data-value");b.multiple&&e.children("option").each(function(b,c){a(c).attr("value")==f&&(a(c).prop("selected",!1),a(c).attr("data-iscustom")&&a(c).remove())}),i(b,c,e),j(e)},l=function(b,c){var d=a(document.getElementById(c.inputId)),e=a(document.getElementById(c.suggestionsId)),f=e.children("[aria-hidden=false]").length;for(b%=f;b<0;)b+=f;var g=a(e.children("[aria-hidden=false]").get(b)),h=a(e.children("[role=option]")).index(g),i=c.suggestionsId+"-"+h;e.children().attr("aria-selected",!1).attr("id",""),g.attr("aria-selected",!0).attr("id",i),d.attr("aria-activedescendant",i);var j=g.offset().top-e.offset().top+e.scrollTop()-e.height()/2;e.animate({scrollTop:j},100)},m=function(b){var c=a(document.getElementById(b.suggestionsId)),d=c.children("[aria-selected=true]"),e=c.children("[aria-hidden=false]").index(d);l(e+1,b)},n=function(b){var c=a(document.getElementById(b.selectionId)),d=c.children("[data-active-selection=true]");if(!d)return void h(0,b);var e=c.children("[aria-selected=true]").index(d);h(e-1,b)},o=function(b){var c=a(document.getElementById(b.selectionId)),d=c.children("[data-active-selection=true]");if(!d)return void h(0,b);var e=c.children("[aria-selected=true]").index(d);h(e+1,b)},p=function(b){var c=a(document.getElementById(b.suggestionsId)),d=c.children("[aria-selected=true]"),e=c.children("[aria-hidden=false]").index(d);l(e-1,b)},q=function(b){var c=a(document.getElementById(b.inputId)),d=a(document.getElementById(b.suggestionsId));c.attr("aria-expanded",!1).attr("aria-activedescendant",b.selectionId),d.hide().attr("aria-hidden",!0)},r=function(b,f,g,h){var i=a(document.getElementById(f.inputId)),j=a(document.getElementById(f.suggestionsId)),k=!1,m=[];h.children("option").each(function(b,c){a(c).prop("selected")!==!0&&(m[m.length]={label:c.innerHTML,value:a(c).attr("value")})});var n=f.caseSensitive?g:g.toLocaleLowerCase(),o=a.extend({options:m},b,f);d.render("core/form_autocomplete_suggestions",o).done(function(d){j.replaceWith(d),j=a(document.getElementById(f.suggestionsId)),j.show().attr("aria-hidden",!1),j.children().each(function(c,d){d=a(d),b.caseSensitive&&d.text().indexOf(n)>-1||!b.caseSensitive&&d.text().toLocaleLowerCase().indexOf(n)>-1?(d.show().attr("aria-hidden",!1),k=!0):d.hide().attr("aria-hidden",!0)}),i.attr("aria-expanded",!0),k?b.tags||l(0,f):c.get_string("nosuggestions","form").done(function(a){j.html(a)})}).fail(e.exception)},s=function(b,c,d){var e=a(document.getElementById(c.inputId)),f=e.val(),g=f.split(","),h=!1;a.each(g,function(c,e){if(e=e.trim(),""!==e&&(b.multiple||d.children("option").prop("selected",!1),d.children("option").each(function(b,c){a(c).attr("value")==e&&(h=!0,a(c).prop("selected",!0))}),!h)){var f=a("<option>");f.append(e),f.attr("value",e),d.append(f),f.prop("selected",!0),f.attr("data-iscustom",!0)}}),i(b,c,d),j(d),e.val(""),q(c)},t=function(b,c,d){var e=a(document.getElementById(c.inputId)),f=a(document.getElementById(c.suggestionsId)),g=f.children("[aria-selected=true]").attr("data-value");b.multiple||d.children("option").prop("selected",!1),d.children("option").each(function(b,c){a(c).attr("value")==g&&a(c).prop("selected",!0)}),i(b,c,d),j(d),b.closeSuggestionsOnSelect?(e.val(""),q(c)):(e.focus(),r(b,c,e.val(),d))},u=function(b,c,d,f,g){var h="form-autocomplete-updateajax";M.util.js_pending(h);var i=a(b.currentTarget).val();g.transport(c.selector,i,function(b){var e=g.processResults(c.selector,b),i=[];if(f.children("option").each(function(b,c){c=a(c),c.prop("selected")?i.push(String(c.attr("value"))):c.remove()}),!c.multiple&&0===f.children("option").length){var j=a("<option>");f.append(j)}a.each(e,function(b,c){if(i.indexOf(String(c.value))===-1){var d=a("<option>");d.append(c.label),d.attr("value",c.value),f.append(d)}}),r(c,d,"",f),M.util.js_complete(h)},function(a){M.util.js_complete(h),e.exception(a)})},v=function(b,c,d){var e=a(document.getElementById(c.inputId));if(e.on("keydown",function(g){var h="form-autocomplete-addnav-"+c.inputId+"-"+g.keyCode;switch(M.util.js_pending(h),g.keyCode){case f.DOWN:return b.showSuggestions?("true"===e.attr("aria-expanded")?m(c):!e.val()&&b.ajax?require([b.ajax],function(a){u(g,b,c,d,a)}):r(b,c,e.val(),d),g.preventDefault(),M.util.js_complete(h),!1):(M.util.js_complete(h),!0);case f.UP:return p(c),g.preventDefault(),M.util.js_complete(h),!1;case f.ENTER:var i=a(document.getElementById(c.suggestionsId));return"true"===e.attr("aria-expanded")&&i.children("[aria-selected=true]").length>0?t(b,c,d):b.tags&&s(b,c,d),g.preventDefault(),M.util.js_complete(h),!1;case f.ESCAPE:return"true"===e.attr("aria-expanded")&&q(c),g.preventDefault(),M.util.js_complete(h),!1}return M.util.js_complete(h),!0}),e.on("keypress",function(a){var e="form-autocomplete-keypress-"+a.keyCode;return M.util.js_pending(e),a.keyCode===f.COMMA?(b.tags&&s(b,c,d),a.preventDefault(),M.util.js_complete(e),!1):(M.util.js_complete(e),!0)}),e.on("behat:set-value",function(){var f=a(document.getElementById(c.suggestionsId)),g="form-autocomplete-behat";M.util.js_pending(g),"true"===e.attr("aria-expanded")&&f.children("[aria-selected=true]").length>0?t(b,c,d):b.tags&&s(b,c,d),M.util.js_complete(g)}),e.on("blur",function(){var f="form-autocomplete-blur";M.util.js_pending(f),window.setTimeout(function(){var g=a(document.activeElement);g.attr("id")!=e.attr("id")&&(b.tags&&s(b,c,d),q(c)),M.util.js_complete(f)},500)}),b.showSuggestions){var g=a(document.getElementById(c.downArrowId));g.on("click",function(a){var f="form-autocomplete-show-suggestions";M.util.js_pending(f),e.focus(),!e.val()&&b.ajax?require([b.ajax],function(e){u(a,b,c,d,e)}):r(b,c,e.val(),d),M.util.js_complete(f)})}var h=a(document.getElementById(c.suggestionsId));h.parent().on("click","[role=option]",function(e){var f="form-autocomplete-parent";M.util.js_pending(f);var g=a(e.currentTarget).closest("[role=option]"),h=a(document.getElementById(c.suggestionsId)),i=h.children("[aria-hidden=false]").index(g);l(i,c),t(b,c,d),M.util.js_complete(f)});var i=a(document.getElementById(c.selectionId));i.on("click","[role=listitem]",function(e){var f="form-autocomplete-clicks";M.util.js_pending(f);var g=a(e.currentTarget);k(b,c,g,d),M.util.js_complete(f)}),i.on("keydown",function(e){var g="form-autocomplete-keydown-"+e.keyCode;switch(M.util.js_pending(g),e.keyCode){case f.DOWN:return o(c),e.preventDefault(),M.util.js_complete(g),!1;case f.UP:return n(c),e.preventDefault(),M.util.js_complete(g),!1;case f.SPACE:case f.ENTER:var h=a(document.getElementById(c.selectionId)).children("[data-active-selection=true]");return h&&(k(b,c,h,d),e.preventDefault()),M.util.js_complete(g),!1}return M.util.js_complete(g),!0}),b.showSuggestions&&(b.ajax?require([b.ajax],function(a){var f=null,g="autocomplete-throttledhandler",h=function(e){u(e,b,c,d,a),M.util.js_complete(g)},i=function(a){null!==f?(window.clearTimeout(f),f=null):M.util.js_pending(g),f=window.setTimeout(h.bind(this,a),300)};e.on("input",i)}):e.on("input",function(e){var f=a(e.currentTarget).val(),g=a(e.currentTarget).data("last-value");g!==f&&r(b,c,f,d),a(e.currentTarget).data("last-value",f)}))};return{enhance:function(f,h,j,k,l,m,n,o){var p={selector:f,tags:!1,ajax:!1,placeholder:k,caseSensitive:!1,showSuggestions:!0,noSelectionString:n},q="autocomplete-setup-"+f;M.util.js_pending(q),"undefined"!=typeof h&&(p.tags=h),"undefined"!=typeof j&&(p.ajax=j),"undefined"!=typeof l&&(p.caseSensitive=l),"undefined"!=typeof m&&(p.showSuggestions=m),"undefined"==typeof n&&c.get_string("noselection","form").done(function(a){p.noSelectionString=a}).fail(e.exception);var r=a(f);if(!r)return b.debug("Selector not found: "+f),M.util.js_complete(q),!1;r.css("visibility","hidden").attr("aria-hidden",!0);var s={selectId:r.attr("id"),inputId:"form_autocomplete_input-"+g,suggestionsId:"form_autocomplete_suggestions-"+g,selectionId:"form_autocomplete_selection-"+g,downArrowId:"form_autocomplete_downarrow-"+g};g++,p.multiple=r.attr("multiple"),"undefined"!=typeof o?p.closeSuggestionsOnSelect=o:p.closeSuggestionsOnSelect=!p.multiple;var t=a("[for="+s.selectId+"]"),u=[];r.children("option").each(function(b,c){u[b]={label:c.innerHTML,value:a(c).attr("value")}});var w=a.extend({},p,s);w.options=u,w.items=[];var x=d.render("core/form_autocomplete_input",w),y=d.render("core/form_autocomplete_suggestions",w),z=d.render("core/form_autocomplete_selection",w);return a.when(x,y,z).then(function(b,c,d){r.hide(),r.after(c),r.after(b),r.after(d),t.attr("for",s.inputId),v(p,s,r);var e=a(document.getElementById(s.suggestionsId));return e.hide().attr("aria-hidden",!0),i(p,s,r),M.util.js_complete(q),!0}).fail(function(a){M.util.js_complete(q),e.exception(a)})}}});
\ No newline at end of file
+define(["jquery","core/log","core/str","core/templates","core/notification"],function(a,b,c,d,e){var f={DOWN:40,ENTER:13,SPACE:32,ESCAPE:27,COMMA:44,UP:38},g=a.now(),h=function(b,c){var d=a(document.getElementById(c.selectionId)),e=d.children("[aria-selected=true]").length;for(b%=e;b<0;)b+=e;var f=a(d.children("[aria-selected=true]").get(b)),g=c.selectionId+"-"+b;d.children().attr("data-active-selection",!1).attr("id",""),f.attr("data-active-selection",!0).attr("id",g),d.attr("aria-activedescendant",g)},i=function(b,c,f){var g=[],i=a(document.getElementById(c.selectionId)),j=i.attr("aria-activedescendant"),k=!1;j&&(k=a(document.getElementById(j)).attr("data-value")),f.children("option").each(function(b,c){if(a(c).prop("selected")){var d;d=a(c).data("html")?a(c).data("html"):a(c).html(),g.push({label:d,value:a(c).attr("value")})}});var l=a.extend({items:g},b,c);d.render("core/form_autocomplete_selection",l).done(function(b){i.empty().append(a(b).html()),k!==!1&&i.children("[aria-selected=true]").each(function(b,d){a(d).attr("data-value")===k&&h(b,c)})}).fail(e.exception)},j=function(a){"undefined"!=typeof M.core_formchangechecker&&M.core_formchangechecker.set_form_changed(),a.change()},k=function(b,c,d,e){var f=a(d).attr("data-value");b.multiple&&e.children("option").each(function(b,c){a(c).attr("value")==f&&(a(c).prop("selected",!1),a(c).attr("data-iscustom")&&a(c).remove())}),i(b,c,e),j(e)},l=function(b,c){var d=a(document.getElementById(c.inputId)),e=a(document.getElementById(c.suggestionsId)),f=e.children("[aria-hidden=false]").length;for(b%=f;b<0;)b+=f;var g=a(e.children("[aria-hidden=false]").get(b)),h=a(e.children("[role=option]")).index(g),i=c.suggestionsId+"-"+h;e.children().attr("aria-selected",!1).attr("id",""),g.attr("aria-selected",!0).attr("id",i),d.attr("aria-activedescendant",i);var j=g.offset().top-e.offset().top+e.scrollTop()-e.height()/2;e.animate({scrollTop:j},100)},m=function(b){var c=a(document.getElementById(b.suggestionsId)),d=c.children("[aria-selected=true]"),e=c.children("[aria-hidden=false]").index(d);l(e+1,b)},n=function(b){var c=a(document.getElementById(b.selectionId)),d=c.children("[data-active-selection=true]");if(!d)return void h(0,b);var e=c.children("[aria-selected=true]").index(d);h(e-1,b)},o=function(b){var c=a(document.getElementById(b.selectionId)),d=c.children("[data-active-selection=true]");if(!d)return void h(0,b);var e=c.children("[aria-selected=true]").index(d);h(e+1,b)},p=function(b){var c=a(document.getElementById(b.suggestionsId)),d=c.children("[aria-selected=true]"),e=c.children("[aria-hidden=false]").index(d);l(e-1,b)},q=function(b){var c=a(document.getElementById(b.inputId)),d=a(document.getElementById(b.suggestionsId));c.attr("aria-expanded",!1).attr("aria-activedescendant",b.selectionId),d.hide().attr("aria-hidden",!0)},r=function(b,f,g,h){var i=a(document.getElementById(f.inputId)),j=a(document.getElementById(f.suggestionsId)),k=!1,m=[];h.children("option").each(function(b,c){a(c).prop("selected")!==!0&&(m[m.length]={label:c.innerHTML,value:a(c).attr("value")})});var n=f.caseSensitive?g:g.toLocaleLowerCase(),o=a.extend({options:m},b,f);d.render("core/form_autocomplete_suggestions",o).done(function(d){j.replaceWith(d),j=a(document.getElementById(f.suggestionsId)),j.show().attr("aria-hidden",!1),j.children().each(function(c,d){d=a(d),b.caseSensitive&&d.text().indexOf(n)>-1||!b.caseSensitive&&d.text().toLocaleLowerCase().indexOf(n)>-1?(d.show().attr("aria-hidden",!1),k=!0):d.hide().attr("aria-hidden",!0)}),i.attr("aria-expanded",!0),k?b.tags||l(0,f):c.get_string("nosuggestions","form").done(function(a){j.html(a)})}).fail(e.exception)},s=function(b,c,d){var e=a(document.getElementById(c.inputId)),f=e.val(),g=f.split(","),h=!1;a.each(g,function(c,e){if(e=e.trim(),""!==e&&(b.multiple||d.children("option").prop("selected",!1),d.children("option").each(function(b,c){a(c).attr("value")==e&&(h=!0,a(c).prop("selected",!0))}),!h)){var f=a("<option>");f.append(e),f.attr("value",e),d.append(f),f.prop("selected",!0),f.attr("data-iscustom",!0)}}),i(b,c,d),j(d),e.val(""),q(c)},t=function(b,c,d){var e=a(document.getElementById(c.inputId)),f=a(document.getElementById(c.suggestionsId)),g=f.children("[aria-selected=true]").attr("data-value");b.multiple||d.children("option").prop("selected",!1),d.children("option").each(function(b,c){a(c).attr("value")==g&&a(c).prop("selected",!0)}),i(b,c,d),j(d),b.closeSuggestionsOnSelect?(e.val(""),q(c)):(e.focus(),r(b,c,e.val(),d))},u=function(b,c,d,f,g){var h="form-autocomplete-updateajax";M.util.js_pending(h);var i=a(b.currentTarget).val();g.transport(c.selector,i,function(b){var e=g.processResults(c.selector,b),i=[];if(f.children("option").each(function(b,c){c=a(c),c.prop("selected")?i.push(String(c.attr("value"))):c.remove()}),!c.multiple&&0===f.children("option").length){var j=a("<option>");f.append(j)}a.each(e,function(b,c){if(i.indexOf(String(c.value))===-1){var d=a("<option>");d.append(c.label),d.attr("value",c.value),f.append(d)}}),r(c,d,"",f),M.util.js_complete(h)},function(a){M.util.js_complete(h),e.exception(a)})},v=function(b,c,d){var e=a(document.getElementById(c.inputId));if(e.on("keydown",function(g){var h="form-autocomplete-addnav-"+c.inputId+"-"+g.keyCode;switch(M.util.js_pending(h),g.keyCode){case f.DOWN:return b.showSuggestions?("true"===e.attr("aria-expanded")?m(c):!e.val()&&b.ajax?require([b.ajax],function(a){u(g,b,c,d,a)}):r(b,c,e.val(),d),g.preventDefault(),M.util.js_complete(h),!1):(M.util.js_complete(h),!0);case f.UP:return p(c),g.preventDefault(),M.util.js_complete(h),!1;case f.ENTER:var i=a(document.getElementById(c.suggestionsId));return"true"===e.attr("aria-expanded")&&i.children("[aria-selected=true]").length>0?t(b,c,d):b.tags&&s(b,c,d),g.preventDefault(),M.util.js_complete(h),!1;case f.ESCAPE:return"true"===e.attr("aria-expanded")&&q(c),g.preventDefault(),M.util.js_complete(h),!1}return M.util.js_complete(h),!0}),e.on("keypress",function(a){var e="form-autocomplete-keypress-"+a.keyCode;return M.util.js_pending(e),a.keyCode===f.COMMA?(b.tags&&s(b,c,d),a.preventDefault(),M.util.js_complete(e),!1):(M.util.js_complete(e),!0)}),e.on("behat:set-value",function(){var f=a(document.getElementById(c.suggestionsId)),g="form-autocomplete-behat";M.util.js_pending(g),"true"===e.attr("aria-expanded")&&f.children("[aria-selected=true]").length>0?t(b,c,d):b.tags&&s(b,c,d),M.util.js_complete(g)}),e.on("blur",function(){var f="form-autocomplete-blur";M.util.js_pending(f),window.setTimeout(function(){var g=a(document.activeElement);g.attr("id")!=e.attr("id")&&(b.tags&&s(b,c,d),q(c)),M.util.js_complete(f)},500)}),b.showSuggestions){var g=a(document.getElementById(c.downArrowId));g.on("click",function(a){var f="form-autocomplete-show-suggestions";M.util.js_pending(f),e.focus(),!e.val()&&b.ajax?require([b.ajax],function(e){u(a,b,c,d,e)}):r(b,c,e.val(),d),M.util.js_complete(f)})}var h=a(document.getElementById(c.suggestionsId));h.parent().on("click","[role=option]",function(e){var f="form-autocomplete-parent";M.util.js_pending(f);var g=a(e.currentTarget).closest("[role=option]"),h=a(document.getElementById(c.suggestionsId)),i=h.children("[aria-hidden=false]").index(g);l(i,c),t(b,c,d),M.util.js_complete(f)});var i=a(document.getElementById(c.selectionId));i.on("click","[role=listitem]",function(e){var f="form-autocomplete-clicks";M.util.js_pending(f);var g=a(e.currentTarget);k(b,c,g,d),M.util.js_complete(f)}),i.on("keydown",function(e){var g="form-autocomplete-keydown-"+e.keyCode;switch(M.util.js_pending(g),e.keyCode){case f.DOWN:return o(c),e.preventDefault(),M.util.js_complete(g),!1;case f.UP:return n(c),e.preventDefault(),M.util.js_complete(g),!1;case f.SPACE:case f.ENTER:var h=a(document.getElementById(c.selectionId)).children("[data-active-selection=true]");return h&&(k(b,c,h,d),e.preventDefault()),M.util.js_complete(g),!1}return M.util.js_complete(g),!0}),b.showSuggestions&&(b.ajax?require([b.ajax],function(a){var f=null,g="autocomplete-throttledhandler",h=function(e){u(e,b,c,d,a),M.util.js_complete(g)},i=function(a){null!==f?(window.clearTimeout(f),f=null):M.util.js_pending(g),f=window.setTimeout(h.bind(this,a),300)};e.on("input",i)}):e.on("input",function(e){var f=a(e.currentTarget).val(),g=a(e.currentTarget).data("last-value");g!==f&&r(b,c,f,d),a(e.currentTarget).data("last-value",f)}))};return{enhance:function(f,h,j,k,l,m,n,o){var p={selector:f,tags:!1,ajax:!1,placeholder:k,caseSensitive:!1,showSuggestions:!0,noSelectionString:n},q="autocomplete-setup-"+f;M.util.js_pending(q),"undefined"!=typeof h&&(p.tags=h),"undefined"!=typeof j&&(p.ajax=j),"undefined"!=typeof l&&(p.caseSensitive=l),"undefined"!=typeof m&&(p.showSuggestions=m),"undefined"==typeof n&&c.get_string("noselection","form").done(function(a){p.noSelectionString=a}).fail(e.exception);var r=a(f);if(!r)return b.debug("Selector not found: "+f),M.util.js_complete(q),!1;r.css("visibility","hidden").attr("aria-hidden",!0);var s={selectId:r.attr("id"),inputId:"form_autocomplete_input-"+g,suggestionsId:"form_autocomplete_suggestions-"+g,selectionId:"form_autocomplete_selection-"+g,downArrowId:"form_autocomplete_downarrow-"+g};g++,p.multiple=r.attr("multiple"),"undefined"!=typeof o?p.closeSuggestionsOnSelect=o:p.closeSuggestionsOnSelect=!p.multiple;var t=a("[for="+s.selectId+"]"),u=[];r.children("option").each(function(b,c){u[b]={label:c.innerHTML,value:a(c).attr("value")}});var w=a.extend({},p,s);w.options=u,w.items=[];var x=d.render("core/form_autocomplete_input",w),y=d.render("core/form_autocomplete_suggestions",w),z=d.render("core/form_autocomplete_selection",w);return a.when(x,y,z).then(function(b,c,d){r.hide(),r.after(c),r.after(b),r.after(d),t.attr("for",s.inputId),v(p,s,r);var e=a(document.getElementById(s.suggestionsId));return e.hide().attr("aria-hidden",!0),i(p,s,r),M.util.js_complete(q),!0}).fail(function(a){M.util.js_complete(q),e.exception(a)})}}});
\ No newline at end of file
diff --git a/lib/amd/src/form-autocomplete.js b/lib/amd/src/form-autocomplete.js
index 29ae07145f863..ea2fab362741a 100644
--- a/lib/amd/src/form-autocomplete.js
+++ b/lib/amd/src/form-autocomplete.js
@@ -92,7 +92,13 @@ define(['jquery', 'core/log', 'core/str', 'core/templates', 'core/notification']
         }
         originalSelect.children('option').each(function(index, ele) {
             if ($(ele).prop('selected')) {
-                items.push({label: $(ele).html(), value: $(ele).attr('value')});
+                var label;
+                if ($(ele).data('html')) {
+                    label = $(ele).data('html');
+                } else {
+                    label = $(ele).html();
+                }
+                items.push({label: label, value: $(ele).attr('value')});
             }
         });
         var context = $.extend({items: items}, options, state);
diff --git a/lib/classes/user.php b/lib/classes/user.php
index 6925e0224f61d..ce986c926caf0 100644
--- a/lib/classes/user.php
+++ b/lib/classes/user.php
@@ -172,6 +172,235 @@ public static function get_user_by_username($username, $fields = '*', $mnethosti
         return $DB->get_record('user', array('username' => $username, 'mnethostid' => $mnethostid), $fields, $strictness);
     }
 
+    /**
+     * Searches for users by name, possibly within a specified context, with current user's access.
+     *
+     * Deciding which users to search is complicated because it relies on user permissions;
+     * ideally, we shouldn't show names if you aren't allowed to see their profile. The permissions
+     * for seeing profile are really complicated.
+     *
+     * Even if search is restricted to a course, it's possible that other people might have
+     * been able to contribute within the course (e.g. they were enrolled before and not now;
+     * or people with system-level roles) so if the user has permission we do want to include
+     * everyone. However, if there are multiple results then we prioritise the ones who are
+     * enrolled in the course.
+     *
+     * If you have moodle/user:viewdetails at system level, you can search everyone.
+     * Otherwise we check which courses you *do* have that permission and search everyone who is
+     * enrolled on those courses.
+     *
+     * Normally you can only search the user's name. If you have the moodle/site:viewuseridentity
+     * capability then we also let you search the fields which are listed as identity fields in
+     * the 'showuseridentity' config option. For example, this might include the user's ID number
+     * or email.
+     *
+     * The $max parameter controls the maximum number of users returned. If users are restricted
+     * from view for some reason, multiple runs of the main query might be made; the $querylimit
+     * parameter allows this to be restricted. Both parameters can be zero to remove limits.
+     *
+     * The returned user objects include id, username, all fields required for user pictures, and
+     * user identity fields.
+     *
+     * @param string $query Search query text
+     * @param \context_course|null $coursecontext Course context or null if system-wide
+     * @param int $max Max number of users to return, default 30 (zero = no limit)
+     * @param int $querylimit Max number of database queries, default 5 (zero = no limit)
+     * @return array Array of user objects with limited fields
+     */
+    public static function search($query, \context_course $coursecontext = null,
+            $max = 30, $querylimit = 5) {
+        global $CFG, $DB;
+        require_once($CFG->dirroot . '/user/lib.php');
+
+        // Allow limits to be turned off.
+        if (!$max) {
+            $max = PHP_INT_MAX;
+        }
+        if (!$querylimit) {
+            $querylimit = PHP_INT_MAX;
+        }
+
+        // Check permission to view profiles at each context.
+        $systemcontext = \context_system::instance();
+        $viewsystem = has_capability('moodle/user:viewdetails', $systemcontext);
+        if ($viewsystem) {
+            $userquery = 'SELECT id FROM {user}';
+            $userparams = [];
+        }
+        if (!$viewsystem) {
+            list($userquery, $userparams) = self::get_enrolled_sql_on_courses_with_capability(
+                    'moodle/user:viewdetails');
+            if (!$userquery) {
+                // No permissions anywhere, return nothing.
+                return [];
+            }
+        }
+
+        // Start building the WHERE clause based on name.
+        list ($where, $whereparams) = users_search_sql($query, 'u', false);
+
+        // We allow users to search with extra identity fields (as well as name) but only if they
+        // have the permission to display those identity fields.
+        $extrasql = '';
+        $extraparams = [];
+
+        if (empty($CFG->showuseridentity)) {
+            // Explode gives wrong result with empty string.
+            $extra = [];
+        } else {
+            $extra = explode(',', $CFG->showuseridentity);
+        }
+
+        // We need the username just to skip guests.
+        $extrafieldlist = $extra;
+        if (!in_array('username', $extra)) {
+            $extrafieldlist[] = 'username';
+        }
+        // The deleted flag will always be false because users_search_sql excludes deleted users,
+        // but it must be present or it causes PHP warnings in some functions below.
+        if (!in_array('deleted', $extra)) {
+            $extrafieldlist[] = 'deleted';
+        }
+        $extrafields = \user_picture::fields('u',
+                array_merge(get_all_user_name_fields(), $extrafieldlist));
+
+        $index = 1;
+        foreach ($extra as $fieldname) {
+            if ($extrasql) {
+                $extrasql .= ' OR ';
+            }
+            $extrasql .= $DB->sql_like('u.' . $fieldname, ':extra' . $index, false);
+            $extraparams['extra' . $index] = $query . '%';
+            $index++;
+        }
+
+        $identitysystem = has_capability('moodle/site:viewuseridentity', $systemcontext);
+        $usingshowidentity = false;
+        if ($identitysystem) {
+            // They have permission everywhere so just add the extra query to the normal query.
+            $where .= ' OR ' . $extrasql;
+            $whereparams = array_merge($whereparams, $extraparams);
+        } else {
+            // Get all courses where user can view full user identity.
+            list($sql, $params) = self::get_enrolled_sql_on_courses_with_capability(
+                    'moodle/site:viewuseridentity');
+            if ($sql) {
+                // Join that with the user query to get an extra field indicating if we can.
+                $userquery = "
+                        SELECT innerusers.id, COUNT(identityusers.id) AS showidentity
+                          FROM ($userquery) innerusers
+                     LEFT JOIN ($sql) identityusers ON identityusers.id = innerusers.id
+                      GROUP BY innerusers.id";
+                $userparams = array_merge($userparams, $params);
+                $usingshowidentity = true;
+
+                // Query on the extra fields only in those places.
+                $where .= ' OR (users.showidentity > 0 AND (' . $extrasql . '))';
+                $whereparams = array_merge($whereparams, $extraparams);
+            }
+        }
+
+        // Default order is just name order. But if searching within a course then we show users
+        // within the course first.
+        list ($order, $orderparams) = users_order_by_sql('u', $query, $systemcontext);
+        if ($coursecontext) {
+            list ($sql, $params) = get_enrolled_sql($coursecontext);
+            $mainfield = 'innerusers2.id';
+            if ($usingshowidentity) {
+                $mainfield .= ', innerusers2.showidentity';
+            }
+            $userquery = "
+                    SELECT $mainfield, COUNT(courseusers.id) AS incourse
+                      FROM ($userquery) innerusers2
+                 LEFT JOIN ($sql) courseusers ON courseusers.id = innerusers2.id
+                  GROUP BY $mainfield";
+            $userparams = array_merge($userparams, $params);
+
+            $order = 'incourse DESC, ' . $order;
+        }
+
+        // Get result (first 30 rows only) from database. Take a couple spare in case we have to
+        // drop some.
+        $result = [];
+        $got = 0;
+        $pos = 0;
+        $readcount = $max + 2;
+        for ($i = 0; $i < $querylimit; $i++) {
+            $rawresult = $DB->get_records_sql("
+                    SELECT users.*, $extrafields
+                      FROM ($userquery) users
+                      JOIN {user} u ON u.id = users.id
+                     WHERE $where
+                  ORDER BY $order", array_merge($userparams, $whereparams, $orderparams),
+                    $pos, $readcount);
+            foreach ($rawresult as $user) {
+                // Skip guest.
+                if ($user->username === 'guest') {
+                    continue;
+                }
+                // Check user can really view profile (there are per-user cases where this could
+                // be different for some reason, this is the same check used by the profile view pages
+                // to double-check that it is OK).
+                if (!user_can_view_profile($user)) {
+                    continue;
+                }
+                $result[] = $user;
+                $got++;
+                if ($got >= $max) {
+                    break;
+                }
+            }
+
+            if ($got >= $max) {
+                // All necessary results obtained.
+                break;
+            }
+            if (count($rawresult) < $readcount) {
+                // No more results from database.
+                break;
+            }
+            $pos += $readcount;
+        }
+
+        return $result;
+    }
+
+    /**
+     * Gets an SQL query that lists all enrolled user ids on any course where the current
+     * user has the specified capability. Helper function used for searching users.
+     *
+     * @param string $capability Required capability
+     * @return array Array containing SQL and params, or two nulls if there are no courses
+     */
+    protected static function get_enrolled_sql_on_courses_with_capability($capability) {
+        // Get all courses where user have the capability.
+        $courses = get_user_capability_course($capability, null, true,
+                'ctxid, ctxpath, ctxdepth, ctxlevel, ctxinstance');
+        if (!$courses) {
+            return [null, null];
+        }
+
+        // Loop around all courses getting the SQL for enrolled users. Note: This query could
+        // probably be more efficient (without the union) if get_enrolled_sql had a way to
+        // pass an array of courseids, but it doesn't.
+        $unionsql = '';
+        $unionparams = [];
+        foreach ($courses as $course) {
+            // Get SQL to list user ids enrolled in this course.
+            \context_helper::preload_from_record($course);
+            list ($sql, $params) = get_enrolled_sql(\context_course::instance($course->id));
+
+            // Combine to a big union query.
+            if ($unionsql) {
+                $unionsql .= ' UNION ';
+            }
+            $unionsql .= $sql;
+            $unionparams = array_merge($unionparams, $params);
+        }
+
+        return [$unionsql, $unionparams];
+    }
+
     /**
      * Helper function to return dummy noreply user record.
      *
diff --git a/lib/db/services.php b/lib/db/services.php
index 3fbf53d11eb58..976108971c710 100644
--- a/lib/db/services.php
+++ b/lib/db/services.php
@@ -1185,6 +1185,13 @@
         'type' => 'write',
         'capabilities' => 'moodle/role:assign'
     ),
+    'core_search_get_relevant_users' => array(
+        'classname' => '\core_search\external',
+        'methodname' => 'get_relevant_users',
+        'description' => 'Gets relevant users for a search request.',
+        'type' => 'read',
+        'ajax' => true
+    ),
     'core_tag_get_tagindex' => array(
         'classname' => 'core_tag_external',
         'methodname' => 'get_tagindex',
diff --git a/lib/form/autocomplete.php b/lib/form/autocomplete.php
index 0e501ab39656b..2be3c40cde5dd 100644
--- a/lib/form/autocomplete.php
+++ b/lib/form/autocomplete.php
@@ -52,6 +52,8 @@ class MoodleQuickForm_autocomplete extends MoodleQuickForm_select {
     protected $showsuggestions = true;
     /** @var string $noselectionstring String that is shown when there are no selections. */
     protected $noselectionstring = '';
+    /** @var callable|null Function to call (with existing value) to render it to HTML */
+    protected $valuehtmlcallback = null;
 
     /**
      * constructor
@@ -95,6 +97,10 @@ public function __construct($elementName=null, $elementLabel=null, $options=null
             $this->casesensitive = $attributes['casesensitive'] ? true : false;
             unset($attributes['casesensitive']);
         }
+        if (isset($attributes['valuehtmlcallback'])) {
+            $this->valuehtmlcallback = $attributes['valuehtmlcallback'];
+            unset($attributes['valuehtmlcallback']);
+        }
         parent::__construct($elementName, $elementLabel, $options, $attributes);
 
         $this->_type = 'autocomplete';
@@ -127,7 +133,23 @@ function toHtml(){
                 $this->placeholder, $this->casesensitive, $this->showsuggestions, $this->noselectionstring));
         }
 
-        return parent::toHTML();
+        $html = parent::toHTML();
+
+        // Hacky bodge to add in the HTML code to the option tag. There is a nicer
+        // version of this code in the new template version (see export_for_template).
+        if ($this->valuehtmlcallback) {
+            $html = preg_replace_callback('~value="([^"]+)"~', function($matches) {
+                $value = html_entity_decode($matches[1]);
+                $htmlvalue = call_user_func($this->valuehtmlcallback, $value);
+                if ($htmlvalue !== false) {
+                    return $matches[0] . ' data-html="' . s($htmlvalue) . '"';
+                } else {
+                    return $matches[0];
+                }
+            }, $html);
+        }
+
+        return $html;
     }
 
     /**
@@ -209,8 +231,6 @@ function onQuickFormEvent($event, $arg, &$caller)
     }
 
     public function export_for_template(renderer_base $output) {
-        global $PAGE;
-
         $this->_generateId();
         $context = parent::export_for_template($output);
         $context['tags'] = !empty($this->tags);
@@ -219,6 +239,15 @@ public function export_for_template(renderer_base $output) {
         $context['casesensitive'] = !empty($this->casesensitive);
         $context['showsuggestions'] = !empty($this->showsuggestions);
         $context['noselectionstring'] = $this->noselectionstring;
+        if ($this->valuehtmlcallback) {
+            foreach ($context['options'] as &$option) {
+                $value = $option['value'];
+                $html = call_user_func($this->valuehtmlcallback, $value);
+                if ($html !== false) {
+                    $option['html'] = $html;
+                }
+            }
+        }
 
         return $context;
     }
diff --git a/lib/tests/user_test.php b/lib/tests/user_test.php
index 8a443efd09687..a36d2e674aff1 100644
--- a/lib/tests/user_test.php
+++ b/lib/tests/user_test.php
@@ -117,6 +117,304 @@ public function test_get_user_by_username() {
         $this->assertFalse(core_user::get_user_by_username('janedoe'));
     }
 
+    public function test_search() {
+        global $DB;
+
+        self::init_search_tests();
+
+        // Set up three courses for test.
+        $generator = $this->getDataGenerator();
+        $course1 = $generator->create_course();
+        $course2 = $generator->create_course();
+        $course3 = $generator->create_course();
+
+        // Manager user in system level.
+        $manager = $generator->create_user(['firstname' => 'Manager', 'lastname' => 'Person',
+                'email' => 'x@x.x']);
+        $systemcontext = \context_system::instance();
+        $generator->role_assign($DB->get_field('role', 'id', ['shortname' => 'manager']),
+                $manager->id, $systemcontext->id);
+
+        // Teachers in one and two courses.
+        $teacher1 = $generator->create_user(['firstname' => 'Alberto', 'lastname' => 'Unwin',
+                'email' => 'a.unwin@x.x']);
+        $generator->enrol_user($teacher1->id, $course1->id, 'teacher');
+        $teacher2and3 = $generator->create_user(['firstname' => 'Alexandra', 'lastname' => 'Penguin',
+                'email' => 'sillypenguin@x.x']);
+        $generator->enrol_user($teacher2and3->id, $course2->id, 'teacher');
+        $generator->enrol_user($teacher2and3->id, $course3->id, 'teacher');
+
+        // Students in each course and some on multiple courses.
+        $student1 = $generator->create_user(['firstname' => 'Amanda', 'lastname' => 'Hodder',
+                'email' => 'hodder_a@x.x']);
+        $generator->enrol_user($student1->id, $course1->id, 'student');
+        $student2 = $generator->create_user(['firstname' => 'Audrey', 'lastname' => 'Methuen',
+                'email' => 'audrey@x.x']);
+        $generator->enrol_user($student2->id, $course2->id, 'student');
+        $student3 = $generator->create_user(['firstname' => 'Austin', 'lastname' => 'Bloomsbury',
+                'email' => 'a.bloomsbury@x.x']);
+        $generator->enrol_user($student3->id, $course3->id, 'student');
+        $student1and2 = $generator->create_user(['firstname' => 'Augustus', 'lastname' => 'Random',
+                'email' => 'random@x.x']);
+        $generator->enrol_user($student1and2->id, $course1->id, 'student');
+        $generator->enrol_user($student1and2->id, $course2->id, 'student');
+        $studentall = $generator->create_user(['firstname' => 'Amelia', 'lastname' => 'House',
+                'email' => 'house@x.x']);
+        $generator->enrol_user($studentall->id, $course1->id, 'student');
+        $generator->enrol_user($studentall->id, $course2->id, 'student');
+        $generator->enrol_user($studentall->id, $course3->id, 'student');
+
+        // Special mixed user (name does not begin with A) is a teacher in one course and student
+        // in another.
+        $mixed = $generator->create_user(['firstname' => 'Xavier', 'lastname' => 'Harper',
+                'email' => 'xh1248@x.x']);
+        $generator->enrol_user($mixed->id, $course1->id, 'student');
+        $generator->enrol_user($mixed->id, $course3->id, 'teacher');
+
+        // As admin user, try searching for somebody at system level by first name, checking the
+        // results.
+        $this->setAdminUser();
+        $result = core_user::search('Amelia');
+        $this->assertCount(1, $result);
+
+        // Check some basic fields, and test other fields are present.
+        $this->assertEquals($studentall->id, $result[0]->id);
+        $this->assertEquals('Amelia', $result[0]->firstname);
+        $this->assertEquals('House', $result[0]->lastname);
+        $this->assertEquals('house@x.x', $result[0]->email);
+        $this->assertEquals(0, $result[0]->deleted);
+        $this->assertObjectHasAttribute('firstnamephonetic', $result[0]);
+        $this->assertObjectHasAttribute('lastnamephonetic', $result[0]);
+        $this->assertObjectHasAttribute('middlename', $result[0]);
+        $this->assertObjectHasAttribute('alternatename', $result[0]);
+        $this->assertObjectHasAttribute('imagealt', $result[0]);
+        $this->assertObjectHasAttribute('username', $result[0]);
+
+        // Now search by lastname, both names, and partials, case-insensitive.
+        $this->assertEquals($result, core_user::search('House'));
+        $this->assertEquals($result, core_user::search('Amelia house'));
+        $this->assertEquals($result, core_user::search('amelI'));
+        $this->assertEquals($result, core_user::search('hoUs'));
+        $this->assertEquals($result, core_user::search('Amelia H'));
+
+        // Admin user can also search by email (full or partial).
+        $this->assertEquals($result, core_user::search('house@x.x'));
+        $this->assertEquals($result, core_user::search('hOuse@'));
+
+        // What if we just search for A? (They all begin with A except the manager.)
+        $result = core_user::search('a');
+        $this->assertCount(7, $result);
+
+        // Au gets us Audrey, Austin, and Augustus - in alphabetical order by surname.
+        $result = core_user::search('au');
+        $this->assertCount(3, $result);
+        $this->assertEquals('Austin', $result[0]->firstname);
+        $this->assertEquals('Audrey', $result[1]->firstname);
+        $this->assertEquals('Augustus', $result[2]->firstname);
+
+        // But if we search within course 2 we'll get Audrey and Augustus first.
+        $course2context = \context_course::instance($course2->id);
+        $result = core_user::search('au', $course2context);
+        $this->assertCount(3, $result);
+        $this->assertEquals('Audrey', $result[0]->firstname);
+        $this->assertEquals('Augustus', $result[1]->firstname);
+        $this->assertEquals('Austin', $result[2]->firstname);
+
+        // Try doing a few searches as manager - we should get the same results and can still
+        // search by email too.
+        $this->setUser($manager);
+        $result = core_user::search('a');
+        $this->assertCount(7, $result);
+        $result = core_user::search('au', $course2context);
+        $this->assertCount(3, $result);
+        $result = core_user::search('house@x.x');
+        $this->assertCount(1, $result);
+
+        // Teacher 1. No site-level permission so can't see users outside the enrolled course.
+        $this->setUser($teacher1);
+        $result = core_user::search('au');
+        $this->assertCount(1, $result);
+        $this->assertEquals('Augustus', $result[0]->firstname);
+
+        // Can still search by email for that user.
+        $result = core_user::search('random@x.x');
+        $this->assertCount(1, $result);
+
+        // Search everyone - teacher can only see four users (including themself).
+        $result = core_user::search('a');
+        $this->assertCount(4, $result);
+
+        // Search within course 2 - you get the same four users (which doesn't include
+        // everyone on that course) but the two on course 2 should be first.
+        $result = core_user::search('a', $course2context);
+        $this->assertCount(4, $result);
+        $this->assertEquals('Amelia', $result[0]->firstname);
+        $this->assertEquals('Augustus', $result[1]->firstname);
+
+        // Other teacher.
+        $this->setUser($teacher2and3);
+        $result = core_user::search('au');
+        $this->assertCount(3, $result);
+
+        $result = core_user::search('a');
+        $this->assertCount(5, $result);
+
+        // Student can only see users on course 3.
+        $this->setUser($student3);
+        $result = core_user::search('a');
+        $this->assertCount(3, $result);
+
+        $result = core_user::search('au');
+        $this->assertCount(1, $result);
+        $this->assertEquals('Austin', $result[0]->firstname);
+
+        // Student cannot search by email.
+        $result = core_user::search('a.bloomsbury@x.x');
+        $this->assertCount(0, $result);
+
+        // Student on all courses can see all the A users.
+        $this->setUser($studentall);
+        $result = core_user::search('a');
+        $this->assertCount(7, $result);
+
+        // Mixed user can see users on courses 1 and 3.
+        $this->setUser($mixed);
+        $result = core_user::search('a');
+        $this->assertCount(6, $result);
+
+        // Mixed user can search by email for students on course 3 but not on course 1.
+        $result = core_user::search('hodder_a@x.x');
+        $this->assertCount(0, $result);
+        $result = core_user::search('house@x.x');
+        $this->assertCount(1, $result);
+    }
+
+    /**
+     * Tests the search() function with limits on the number to return.
+     */
+    public function test_search_with_count() {
+        self::init_search_tests();
+        $generator = $this->getDataGenerator();
+        $course = $generator->create_course();
+
+        // Check default limit (30).
+        for ($i = 0; $i < 31; $i++) {
+            $student = $generator->create_user(['firstname' => 'Guy', 'lastname' => 'Xxx' . $i,
+                    'email' => 'xxx@x.x']);
+            $generator->enrol_user($student->id, $course->id, 'student');
+        }
+        $this->setAdminUser();
+        $result = core_user::search('Guy');
+        $this->assertCount(30, $result);
+
+        // Check a small limit.
+        $result = core_user::search('Guy', null, 10);
+        $this->assertCount(10, $result);
+
+        // Check no limit.
+        $result = core_user::search('Guy', null, 0);
+        $this->assertCount(31, $result);
+    }
+
+    /**
+     * When course is in separate groups mode and user is a student, they can't see people who
+     * are not in the same group. This is checked by the user profile permission thing and not
+     * currently by the original query.
+     */
+    public function test_search_group_permissions() {
+        global $DB;
+
+        self::init_search_tests();
+
+        // Create one user to do the searching.
+        $generator = $this->getDataGenerator();
+        $course = $generator->create_course(['groupmode' => SEPARATEGROUPS]);
+        $searcher = $generator->create_user(['firstname' => 'Searchy', 'lastname' => 'Sam',
+                'email' => 'xxx@x.x']);
+        $generator->enrol_user($searcher->id, $course->id, 'student');
+        $group = $generator->create_group(['courseid' => $course->id]);
+        groups_add_member($group, $searcher);
+
+        // Create a large number of people so that we have to make multiple database reads.
+        $targets = [];
+        for ($i = 0; $i < 50; $i++) {
+            $student = $generator->create_user(['firstname' => 'Guy', 'lastname' => 'Xxx' . $i,
+                    'email' => 'xxx@x.x']);
+            $generator->enrol_user($student->id, $course->id, 'student');
+            $targets[] = $student;
+        }
+
+        // The first and last people are in the same group.
+        groups_add_member($group, $targets[0]);
+        groups_add_member($group, $targets[49]);
+
+        // As searcher, we only find the 2 in the same group.
+        $this->setUser($searcher);
+        $result = core_user::search('Guy');
+        $this->assertCount(2, $result);
+
+        // If we change the course to visible groups though, we get the max number.
+        $DB->set_field('course', 'groupmode', VISIBLEGROUPS, ['id' => $course->id]);
+        $result = core_user::search('Guy');
+        $this->assertCount(30, $result);
+    }
+
+    /**
+     * When course is in separate groups mode and user is a student, they can't see people who
+     * are not in the same group. This is checked by the user profile permission thing and not
+     * currently by the original query.
+     */
+    public function test_search_deleted_users() {
+        self::init_search_tests();
+
+        // Create one user to do the searching.
+        $generator = $this->getDataGenerator();
+        $course = $generator->create_course();
+        $searcher = $generator->create_user(['firstname' => 'Searchy', 'lastname' => 'Sam',
+                'email' => 'xxx@x.x']);
+        $generator->enrol_user($searcher->id, $course->id, 'student');
+
+        // Create another two users to search for.
+        $student1 = $generator->create_user(['firstname' => 'Amelia', 'lastname' => 'Aardvark']);
+        $student2 = $generator->create_user(['firstname' => 'Amelia', 'lastname' => 'Beetle']);
+        $generator->enrol_user($student1->id, $course->id, 'student');
+        $generator->enrol_user($student2->id, $course->id, 'student');
+
+        // As searcher, we find both users.
+        $this->setUser($searcher);
+        $result = core_user::search('Amelia');
+        $this->assertCount(2, $result);
+
+        // What if one is deleted?
+        delete_user($student1);
+        $result = core_user::search('Amelia');
+        $this->assertCount(1, $result);
+        $this->assertEquals('Beetle', $result[0]->lastname);
+
+        // Delete the other, for good measure.
+        delete_user($student2);
+        $result = core_user::search('Amelia');
+        $this->assertCount(0, $result);
+    }
+
+    /**
+     * Carries out standard setup for the search test functions.
+     */
+    protected static function init_search_tests() {
+        global $DB;
+
+        // For all existing users, set their name and email to something stupid so we don't
+        // accidentally find one, confusing the test counts.
+        $DB->set_field('user', 'firstname', 'Zaphod');
+        $DB->set_field('user', 'lastname', 'Beeblebrox');
+        $DB->set_field('user', 'email', 'zaphod@beeblebrox.example.org');
+
+        // This is the default value, but let's set it just to be certain in case it changes later.
+        // It affects what fields admin (and other users with the viewuseridentity permission) can
+        // search in addition to the name.
+        set_config('showuseridentity', 'email');
+    }
+
     /**
      * Test require_active_user
      */
diff --git a/search/amd/build/form-search-user-selector.min.js b/search/amd/build/form-search-user-selector.min.js
new file mode 100644
index 0000000000000..a6eee77c0426f
--- /dev/null
+++ b/search/amd/build/form-search-user-selector.min.js
@@ -0,0 +1 @@
+define(["jquery","core/ajax","core/templates"],function(a,b,c){return{processResults:function(b,c){var d=[];return a.each(c,function(a,b){d.push({value:b.id,label:b._label})}),d},transport:function(d,e,f,g){var h,i={query:e},j=a(d).attr("withincourseid");"undefined"!=typeof j&&""!==a("#id_searchwithin").val()?i.courseid=j:i.courseid=0,h=b.call([{methodname:"core_search_get_relevant_users",args:i}]),h[0].then(function(b){var d=[];return a.each(b,function(a,b){d.push(c.render("core_search/form-user-selector-suggestion",b))}),a.when.apply(a.when,d).then(function(){var c=arguments,d=0;a.each(b,function(a,b){b._label=c[d++]}),f(b)})}).fail(g)}}});
\ No newline at end of file
diff --git a/search/amd/src/form-search-user-selector.js b/search/amd/src/form-search-user-selector.js
new file mode 100644
index 0000000000000..fc694d33a5f70
--- /dev/null
+++ b/search/amd/src/form-search-user-selector.js
@@ -0,0 +1,82 @@
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Search user selector module.
+ *
+ * @module core_search/form-search-user-selector
+ * @class form-search-user-selector
+ * @package core_search
+ * @copyright 2017 The Open University
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+define(['jquery', 'core/ajax', 'core/templates'], function($, Ajax, Templates) {
+
+    return /** @alias module:core_search/form-search-user-selector */ {
+
+        processResults: function(selector, results) {
+            var users = [];
+            $.each(results, function(index, user) {
+                users.push({
+                    value: user.id,
+                    label: user._label
+                });
+            });
+            return users;
+        },
+
+        transport: function(selector, query, success, failure) {
+            var promise;
+
+            // Search within specific course if known and if the 'search within' dropdown is set
+            // to search within course or activity.
+            var args = {query: query};
+            var courseid = $(selector).attr('withincourseid');
+            if (typeof courseid !== "undefined" && $('#id_searchwithin').val() !== '') {
+                args.courseid = courseid;
+            } else {
+                args.courseid = 0;
+            }
+
+            // Call AJAX request.
+            promise = Ajax.call([{methodname: 'core_search_get_relevant_users', args: args}]);
+
+            // When AJAX request returns, handle the results.
+            promise[0].then(function(results) {
+                var promises = [];
+
+                // Render label with user name and picture.
+                $.each(results, function(index, user) {
+                    promises.push(Templates.render('core_search/form-user-selector-suggestion', user));
+                });
+
+                // Apply the label to the results.
+                return $.when.apply($.when, promises).then(function() {
+                    var args = arguments;
+                    var i = 0;
+                    $.each(results, function(index, user) {
+                        user._label = args[i++];
+                    });
+                    success(results);
+                    return;
+                });
+
+            }).fail(failure);
+        }
+
+    };
+
+});
diff --git a/search/classes/engine.php b/search/classes/engine.php
index 433b994c8d7d9..3b6207594fb84 100644
--- a/search/classes/engine.php
+++ b/search/classes/engine.php
@@ -589,4 +589,17 @@ public function supports_group_filtering() {
     public function get_supported_orders(\context $context) {
         return ['relevance' => get_string('order_relevance', 'search')];
     }
+
+    /**
+     * Checks if the search engine supports searching by user.
+     *
+     * If it returns true to this function, the search engine should support the 'userids' option
+     * in the $filters value passed to execute_query(), returning only items where the userid in
+     * the search document matches one of those user ids.
+     *
+     * @return bool True if the search engine supports searching by user
+     */
+    public function supports_users() {
+        return false;
+    }
 }
diff --git a/search/classes/external.php b/search/classes/external.php
new file mode 100644
index 0000000000000..ce29bb2f03214
--- /dev/null
+++ b/search/classes/external.php
@@ -0,0 +1,119 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Handles external (web service) function calls related to search.
+ *
+ * @package core_search
+ * @copyright 2017 The Open University
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core_search;
+
+use core_user\external\user_summary_exporter;
+use \external_value;
+use \external_single_structure;
+use \external_multiple_structure;
+
+defined('MOODLE_INTERNAL') || die();
+
+global $CFG;
+require_once($CFG->libdir . '/externallib.php');
+
+/**
+ * Handles external (web service) function calls related to search.
+ *
+ * @package core_search
+ * @copyright 2017 The Open University
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class external extends \external_api {
+    /**
+     * Returns parameter types for get_relevant_users function.
+     *
+     * @return \external_function_parameters Parameters
+     */
+    public static function get_relevant_users_parameters() {
+        return new \external_function_parameters([
+                'query' => new external_value(PARAM_RAW,
+                    'Query string (full or partial user full name or other details)'),
+                'courseid' => new external_value(PARAM_INT, 'Course id (0 if none)'),
+                ]);
+    }
+
+    /**
+     * Returns result type for get_relevant_users function.
+     *
+     * @return \external_description Result type
+     */
+    public static function get_relevant_users_returns() {
+        return new external_multiple_structure(
+                new external_single_structure([
+                    'id' => new external_value(PARAM_INT, 'User id'),
+                    'fullname' => new external_value(PARAM_RAW, 'Full name as text'),
+                    'profileimageurlsmall' => new external_value(PARAM_URL, 'URL to small profile image')
+                ]));
+    }
+
+    /**
+     * Searches for users given a query, taking into account the current user's permissions and
+     * possibly a course to check within.
+     *
+     * @param string $query Query text
+     * @param int $courseid Course id or 0 if no restriction
+     * @return array Defined return structure
+     */
+    public static function get_relevant_users($query, $courseid) {
+        global $CFG, $PAGE;
+
+        // Validate parameter.
+        self::validate_parameters(self::get_relevant_users_parameters(),
+                ['query' => $query, 'courseid' => $courseid]);
+
+        // Validate the context (search page is always system context).
+        $systemcontext = \context_system::instance();
+        self::validate_context($systemcontext);
+
+        // Get course object too.
+        if ($courseid) {
+            $coursecontext = \context_course::instance($courseid);
+        } else {
+            $coursecontext = null;
+        }
+
+        // If not logged in, can't see anyone when forceloginforprofiles is on.
+        if (!empty($CFG->forceloginforprofiles)) {
+            if (!isloggedin() || isguestuser()) {
+                return [];
+            }
+        }
+
+        $users = \core_user::search($query, $coursecontext);
+
+        $result = [];
+        foreach ($users as $user) {
+            // Get a standard exported user object.
+            $fulldetails = (new user_summary_exporter($user))->export($PAGE->get_renderer('core'));
+
+            // To avoid leaking private data to students, only include the specific information we
+            // are going to display (and not the email, idnumber, etc).
+            $result[] = (object)['id' => $fulldetails->id, 'fullname' => $fulldetails->fullname,
+                    'profileimageurlsmall' => $fulldetails->profileimageurlsmall];
+        }
+        return $result;
+    }
+}
diff --git a/search/classes/manager.php b/search/classes/manager.php
index 0f5a7f9c5d80a..9a9fccb049738 100644
--- a/search/classes/manager.php
+++ b/search/classes/manager.php
@@ -720,6 +720,7 @@ public function paged_search(\stdClass $formdata, $pagenum) {
      * - contextids (optional list of context ids to restrict)
      * - context (Moodle context object for location user searched from)
      * - order (optional ordering, one of the types supported by the search engine e.g. 'relevance')
+     * - userids (optional list of user ids to restrict)
      *
      * @param \stdClass $formdata Query input data (usually from search form)
      * @param int $limit The maximum number of documents to return
diff --git a/search/classes/output/form/search.php b/search/classes/output/form/search.php
index 1f4a3b69e1aef..8d633df60be8a 100644
--- a/search/classes/output/form/search.php
+++ b/search/classes/output/form/search.php
@@ -27,6 +27,7 @@
 defined('MOODLE_INTERNAL') || die;
 
 require_once($CFG->libdir . '/formslib.php');
+require_once($CFG->libdir . '/externallib.php');
 
 class search extends \moodleform {
 
@@ -36,7 +37,7 @@ class search extends \moodleform {
      * @return void
      */
     function definition() {
-        global $USER;
+        global $USER, $DB, $OUTPUT;
 
         $mform =& $this->_form;
         $mform->disable_form_change_checker();
@@ -95,6 +96,31 @@ function definition() {
         $mform->addElement('course', 'courseids', get_string('courses', 'core'), $options);
         $mform->setType('courseids', PARAM_INT);
 
+        // If the search engine can search by user, and the user is logged in (so we have
+        // permission to call the user-listing web service) then show the user selector.
+        if ($search->get_engine()->supports_users() && isloggedin()) {
+            $options = [
+                'ajax' => 'core_search/form-search-user-selector',
+                'multiple' => true,
+                'noselectionstring' => get_string('allusers', 'search'),
+                'valuehtmlcallback' => function($value) {
+                    global $DB, $OUTPUT;
+                    $user = $DB->get_record('user', ['id' => (int)$value], '*', IGNORE_MISSING);
+                    if (!$user || !user_can_view_profile($user)) {
+                        return false;
+                    }
+                    $details = user_get_user_details($user);
+                    return $OUTPUT->render_from_template(
+                            'core_search/form-user-selector-suggestion', $details);
+                }
+            ];
+            if (!empty($this->_customdata['withincourseid'])) {
+                $options['withincourseid'] = $this->_customdata['withincourseid'];
+            }
+
+            $mform->addElement('autocomplete', 'userids', get_string('users'), [], $options);
+        }
+
         if (!empty($this->_customdata['searchwithin'])) {
             // Course options should be hidden if we choose to search within a specific location.
             $mform->hideIf('courseids', 'searchwithin', 'ne', '');
diff --git a/search/engine/solr/classes/engine.php b/search/engine/solr/classes/engine.php
index 27ccf7e1eae4a..21199d486fec6 100644
--- a/search/engine/solr/classes/engine.php
+++ b/search/engine/solr/classes/engine.php
@@ -290,6 +290,9 @@ protected function create_user_query($filters, $accessinfo) {
         if (!empty($data->groupids)) {
             $query->addFilterQuery('{!cache=false}groupid:(' . implode(' OR ', $data->groupids) . ')');
         }
+        if (!empty($data->userids)) {
+            $query->addFilterQuery('{!cache=false}userid:(' . implode(' OR ', $data->userids) . ')');
+        }
 
         if (!empty($data->timestart) or !empty($data->timeend)) {
             if (empty($data->timestart)) {
@@ -1399,4 +1402,13 @@ public function get_supported_orders(\context $context) {
 
         return $orders;
     }
+
+    /**
+     * Solr supports search by user id.
+     *
+     * @return bool True
+     */
+    public function supports_users() {
+        return true;
+    }
 }
diff --git a/search/engine/solr/tests/engine_test.php b/search/engine/solr/tests/engine_test.php
index 95240f14f6e78..1cdef7849e740 100644
--- a/search/engine/solr/tests/engine_test.php
+++ b/search/engine/solr/tests/engine_test.php
@@ -935,6 +935,80 @@ public function test_groups() {
                 ['F1NG', 'F1SG-A', 'F1SG-B', 'F1VG-A', 'F1VG-B', 'F2SG-A', 'F2SG-B'], $results);
     }
 
+    /**
+     * Tests searching for results restricted to specific user id(s).
+     */
+    public function test_user_restriction() {
+        // Use real search areas.
+        $this->search->clear_static();
+        $this->search->add_core_search_areas();
+
+        // Create a course, a forum, and a glossary.
+        $generator = $this->getDataGenerator();
+        $course = $generator->create_course();
+        $forum = $generator->create_module('forum', ['course' => $course->id]);
+        $glossary = $generator->create_module('glossary', ['course' => $course->id]);
+
+        // Create 3 user accounts, all enrolled as students on the course.
+        $user1 = $generator->create_user();
+        $user2 = $generator->create_user();
+        $user3 = $generator->create_user();
+        $generator->enrol_user($user1->id, $course->id, 'student');
+        $generator->enrol_user($user2->id, $course->id, 'student');
+        $generator->enrol_user($user3->id, $course->id, 'student');
+
+        // All users create a forum discussion.
+        $forumgen = $generator->get_plugin_generator('mod_forum');
+        $forumgen->create_discussion(['course' => $course->id, 'forum' => $forum->id,
+            'userid' => $user1->id, 'name' => 'Post1', 'message' => 'plugh']);
+        $forumgen->create_discussion(['course' => $course->id, 'forum' => $forum->id,
+                'userid' => $user2->id, 'name' => 'Post2', 'message' => 'plugh']);
+        $forumgen->create_discussion(['course' => $course->id, 'forum' => $forum->id,
+                'userid' => $user3->id, 'name' => 'Post3', 'message' => 'plugh']);
+
+        // Two of the users create entries in the glossary.
+        $glossarygen = $generator->get_plugin_generator('mod_glossary');
+        $glossarygen->create_content($glossary, ['concept' => 'Entry1', 'definition' => 'plugh',
+                'userid' => $user1->id]);
+        $glossarygen->create_content($glossary, ['concept' => 'Entry3', 'definition' => 'plugh',
+                'userid' => $user3->id]);
+
+        // Index the data.
+        $this->search->index();
+
+        // Search without user restriction should find everything.
+        $querydata = new stdClass();
+        $querydata->q = 'plugh';
+        $results = $this->search->search($querydata);
+        $this->assert_result_titles(
+                ['Entry1', 'Entry3', 'Post1', 'Post2', 'Post3'], $results);
+
+        // Restriction to user 3 only.
+        $querydata->userids = [$user3->id];
+        $results = $this->search->search($querydata);
+        $this->assert_result_titles(
+                ['Entry3', 'Post3'], $results);
+
+        // Restriction to users 1 and 2.
+        $querydata->userids = [$user1->id, $user2->id];
+        $results = $this->search->search($querydata);
+        $this->assert_result_titles(
+                ['Entry1', 'Post1', 'Post2'], $results);
+
+        // Restriction to users 1 and 2 combined with context restriction.
+        $querydata->contextids = [context_module::instance($glossary->cmid)->id];
+        $results = $this->search->search($querydata);
+        $this->assert_result_titles(
+                ['Entry1'], $results);
+
+        // Restriction to users 1 and 2 combined with area restriction.
+        unset($querydata->contextids);
+        $querydata->areaids = [\core_search\manager::generate_areaid('mod_forum', 'post')];
+        $results = $this->search->search($querydata);
+        $this->assert_result_titles(
+                ['Post1', 'Post2'], $results);
+    }
+
     /**
      * Asserts that the returned documents have the expected titles (regardless of order).
      *
diff --git a/search/templates/form-user-selector-suggestion.mustache b/search/templates/form-user-selector-suggestion.mustache
new file mode 100644
index 0000000000000..08a5912470abf
--- /dev/null
+++ b/search/templates/form-user-selector-suggestion.mustache
@@ -0,0 +1,41 @@
+{{!
+    This file is part of Moodle - http://moodle.org/
+
+    Moodle is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    Moodle is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+}}
+{{!
+    @template core_search/form-user-selector-suggestion
+
+    Moodle template for the list of valid options in an autocomplate form element.
+
+    Classes required for JS:
+    * none
+
+    Data attributes required for JS:
+    * none
+
+    Context variables required for this template:
+    * profileimageurlsmall Url to a small profile image.
+    * fullname Users full name
+
+    Example context (json):
+    { "id": "1",
+      "fullname": "Kermit Thefrog",
+      "profileimageurlsmall": "https://example.org/img"
+    }
+}}
+<span>
+    <img height="12" src="{{profileimageurlsmall}}" alt="" role="presentation">
+    <span>{{fullname}}</span>
+</span>
diff --git a/search/tests/behat/search_by_user.feature b/search/tests/behat/search_by_user.feature
new file mode 100644
index 0000000000000..37f7f13d2a8f9
--- /dev/null
+++ b/search/tests/behat/search_by_user.feature
@@ -0,0 +1,67 @@
+@core @core_search
+Feature: Select users when searching for user-created content
+  In order to search for content by specific users
+  As a user
+  I need to be able to add users to the select list in the search form
+
+  Background:
+    Given the following config values are set as admin:
+      | enableglobalsearch | 1    |
+      | searchengine       | solr |
+    And the following "courses" exist:
+      | shortname | fullname |
+      | C1        | Frogs    |
+      | C2        | Zombies  |
+    And the following "activities" exist:
+      | activity | name       | intro      | course | idnumber |
+      | page     | PageName1  | PageDesc1  | C1     | PAGE1    |
+    And the following "users" exist:
+      | username | firstname | lastname   |
+      | s1       | Anne      | Other      |
+      | s2       | Anne      | Additional |
+      | t        | Anne      | Ditin      |
+    And the following "course enrolments" exist:
+      | user | course | role    |
+      | s1   | C1     | student |
+      | s2   | C2     | student |
+      | t    | C1     | teacher |
+
+  @javascript
+  Scenario: As administrator, search for users from home page
+    Given I log in as "admin"
+    And global search expects the query "frogs" and will return:
+      | type     | idnumber |
+      | activity | PAGE1    |
+    And I search for "frogs" using the header global search box
+    And I expand all fieldsets
+    And I set the field with xpath "//select[@id='id_userids']/../input[@type='text']" to "Anne"
+    # Alphabetical surname order.
+    Then "Anne Additional" "text" should appear before "Anne Ditin" "text"
+    And "Anne Ditin" "text" should appear before "Anne Other" "text"
+
+  @javascript
+  Scenario: As administrator, search for users within course
+    Given I log in as "admin"
+    And I am on "Frogs" course homepage
+    And global search expects the query "frogs" and will return:
+      | type     | idnumber |
+      | activity | PAGE1    |
+    And I search for "frogs" using the header global search box
+    And I expand all fieldsets
+    And I select "Course: Frogs" from the "Search within" singleselect
+    And I set the field with xpath "//select[@id='id_userids']/../input[@type='text']" to "Anne"
+    # Users in selected course appear first.
+    And "Anne Additional" "text" should appear after "Anne Other" "text"
+
+  @javascript
+  Scenario: As student, cannot see users on other courses
+    Given I log in as "s1"
+    And I am on "Frogs" course homepage
+    And global search expects the query "frogs" and will return:
+      | type     | idnumber |
+      | activity | PAGE1    |
+    And I search for "frogs" using the header global search box
+    And I expand all fieldsets
+    And I set the field with xpath "//select[@id='id_userids']/../input[@type='text']" to "A"
+    Then "Anne Ditin" "text" should appear before "Anne Other" "text"
+    And "Anne Additional" "text" should not exist
diff --git a/search/tests/external_test.php b/search/tests/external_test.php
new file mode 100644
index 0000000000000..fd4fc411b3821
--- /dev/null
+++ b/search/tests/external_test.php
@@ -0,0 +1,72 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * External function unit tests.
+ *
+ * @package core_search
+ * @copyright 2017 The Open University
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core_search;
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * External function unit tests.
+ *
+ * @package core_search
+ * @copyright 2017 The Open University
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class external_testcase extends \advanced_testcase {
+
+    public function setUp() {
+        $this->resetAfterTest();
+    }
+
+    /**
+     * Checks the get_relevant_users function used when selecting users in search filter.
+     */
+    public function test_get_relevant_users() {
+        // Set up two users to search for and one to do the searching.
+        $generator = $this->getDataGenerator();
+        $student1 = $generator->create_user(['firstname' => 'Amelia', 'lastname' => 'Aardvark']);
+        $student2 = $generator->create_user(['firstname' => 'Amelia', 'lastname' => 'Beetle']);
+        $student3 = $generator->create_user(['firstname' => 'Zebedee', 'lastname' => 'Boing']);
+        $course = $generator->create_course();
+        $generator->enrol_user($student1->id, $course->id, 'student');
+        $generator->enrol_user($student2->id, $course->id, 'student');
+        $generator->enrol_user($student3->id, $course->id, 'student');
+
+        // As student 3, search for the other two.
+        $this->setUser($student3);
+        $result = external::get_relevant_users('Amelia', 0);
+        $this->assertCount(2, $result);
+
+        // Check that the result contains all the expected fields.
+        $this->assertEquals($student1->id, $result[0]->id);
+        $this->assertEquals('Amelia Aardvark', $result[0]->fullname);
+        $this->assertContains('/u/f2', $result[0]->profileimageurlsmall);
+
+        // Check we aren't leaking information about user email address (for instance).
+        $this->assertObjectNotHasAttribute('email', $result[0]);
+
+        // Note: We are not checking search permissions, search by different fields, etc. as these
+        // are covered by the core_user::search unit test.
+    }
+}
diff --git a/search/upgrade.txt b/search/upgrade.txt
index 5cf2eeb15e813..b355730cd5839 100644
--- a/search/upgrade.txt
+++ b/search/upgrade.txt
@@ -36,6 +36,11 @@ information provided here is intended especially for developers.
 * API function \core_search\manager::instance() now includes a $fast parameter to skip schema
   checks (as above).
 
+* Search engines should now implement the 'userids' option to restrict search results to those from
+  specific users, and return true to the new supports_users() function. The supplied Solr search
+  engine includes this feature. If this is not implemented, the search engine will continue to work
+  but the 'Users' search option will not appear.
+
 === 3.4 ===
 
 * Search indexing now supports time limits to make the scheduled task run more neatly. In order for
diff --git a/theme/boost/templates/core_form/element-autocomplete.mustache b/theme/boost/templates/core_form/element-autocomplete.mustache
index cd16f7caa0447..a7fea2cc3c5df 100644
--- a/theme/boost/templates/core_form/element-autocomplete.mustache
+++ b/theme/boost/templates/core_form/element-autocomplete.mustache
@@ -9,7 +9,7 @@
             {{/error}}
             {{{element.attributes}}} >
             {{#element.options}}
-            <option value="{{value}}" {{#selected}}selected{{/selected}}>{{{text}}}</option>
+            <option value="{{value}}" {{#selected}}selected{{/selected}}{{#html}} data-html="{{html}}"{{/html}}>{{{text}}}</option>
             {{/element.options}}
         </select>
         {{/element.frozen}}