diff --git a/CHANGES.md b/CHANGES.md
index 98b76d672f1..0046b19832f 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -20,6 +20,7 @@ Fixed Issues:
 * [#12281](http://dev.ckeditor.com/ticket/12281): Fixed: Minor syntax issue in CSS files.
 * [#12178](http://dev.ckeditor.com/ticket/12178): [Blink/Webkit] Fixed: Iterator does not return block if selection is located at the end of it.
 * [#12185](http://dev.ckeditor.com/ticket/12185): [IE9QM] Fixed: Error thrown when moving mouse over focused editor's scrollbar.
+* [#12215](http://dev.ckeditor.com/ticket/12215): Fixed: Basepath resolution doesn't recognize semicolon as a query separator.
 
 Other Changes:
 
diff --git a/ckeditor.js b/ckeditor.js
index abb087d1565..76eb14f169b 100644
--- a/ckeditor.js
+++ b/ckeditor.js
@@ -5,7 +5,10 @@
 
 // Compressed version of core/ckeditor_base.js. See original for instructions.
 /*jsl:ignore*/
-window.CKEDITOR||(window.CKEDITOR=function(){var b={timestamp:"",version:"%VERSION%",revision:"%REV%",rnd:Math.floor(900*Math.random())+100,_:{pending:[]},status:"unloaded",basePath:function(){var a=window.CKEDITOR_BASEPATH||"";if(!a)for(var b=document.getElementsByTagName("script"),c=0;c<b.length;c++){var d=b[c].src.match(/(^|.*[\\\/])ckeditor(?:_basic)?(?:_source)?.js(?:\?.*)?$/i);if(d){a=d[1];break}}-1==a.indexOf(":/")&&"//"!=a.slice(0,2)&&(a=0===a.indexOf("/")?location.href.match(/^.*?:\/\/[^\/]*/)[0]+a:location.href.match(/^[^\?]*\/(?:)/)[0]+a);if(!a)throw'The CKEditor installation path could not be automatically detected. Please set the global variable "CKEDITOR_BASEPATH" before creating editor instances.';return a}(),getUrl:function(a){-1==a.indexOf(":/")&&0!==a.indexOf("/")&&(a=this.basePath+a);this.timestamp&&"/"!=a.charAt(a.length-1)&&!/[&?]t=/.test(a)&&(a+=(0<=a.indexOf("?")?"&":"?")+"t="+this.timestamp);return a},domReady:function(){function a(){try{document.addEventListener?(document.removeEventListener("DOMContentLoaded",a,!1),b()):document.attachEvent&&"complete"===document.readyState&&(document.detachEvent("onreadystatechange",a),b())}catch(d){}}function b(){for(var a;a=c.shift();)a()}var c=[];return function(b){c.push(b);"complete"===document.readyState&&setTimeout(a,1);if(1==c.length)if(document.addEventListener)document.addEventListener("DOMContentLoaded",a,!1),window.addEventListener("load",a,!1);else if(document.attachEvent){document.attachEvent("onreadystatechange",a);window.attachEvent("onload",a);b=!1;try{b=!window.frameElement}catch(e){}if(document.documentElement.doScroll&&b){var f=function(){try{document.documentElement.doScroll("left")}catch(b){setTimeout(f,1);return}a()};f()}}}}()},e=window.CKEDITOR_GETURL;if(e){var g=b.getUrl;b.getUrl=function(a){return e.call(b,a)||g.call(b,a)}}return b}());
+window.CKEDITOR||(window.CKEDITOR=function(){var e=/(^|.*[\\\/])ckeditor\.js(?:\?.*|;.*)?$/i,b={timestamp:"",version:"%VERSION%",revision:"%REV%",rnd:Math.floor(900*Math.random())+100,_:{pending:[],basePathSrcPattern:e},status:"unloaded",basePath:function(){var a=window.CKEDITOR_BASEPATH||"";if(!a)for(var b=document.getElementsByTagName("script"),c=0;c<b.length;c++){var f=b[c].src.match(e);if(f){a=f[1];break}}-1==a.indexOf(":/")&&"//"!=a.slice(0,2)&&(a=0===a.indexOf("/")?location.href.match(/^.*?:\/\/[^\/]*/)[0]+
+a:location.href.match(/^[^\?]*\/(?:)/)[0]+a);if(!a)throw'The CKEditor installation path could not be automatically detected. Please set the global variable "CKEDITOR_BASEPATH" before creating editor instances.';return a}(),getUrl:function(a){-1==a.indexOf(":/")&&0!==a.indexOf("/")&&(a=this.basePath+a);this.timestamp&&"/"!=a.charAt(a.length-1)&&!/[&?]t=/.test(a)&&(a+=(0<=a.indexOf("?")?"&":"?")+"t="+this.timestamp);return a},domReady:function(){function a(){try{document.addEventListener?(document.removeEventListener("DOMContentLoaded",
+a,!1),b()):document.attachEvent&&"complete"===document.readyState&&(document.detachEvent("onreadystatechange",a),b())}catch(f){}}function b(){for(var a;a=c.shift();)a()}var c=[];return function(b){c.push(b);"complete"===document.readyState&&setTimeout(a,1);if(1==c.length)if(document.addEventListener)document.addEventListener("DOMContentLoaded",a,!1),window.addEventListener("load",a,!1);else if(document.attachEvent){document.attachEvent("onreadystatechange",a);window.attachEvent("onload",a);b=!1;try{b=
+!window.frameElement}catch(e){}if(document.documentElement.doScroll&&b){var d=function(){try{document.documentElement.doScroll("left")}catch(b){setTimeout(d,1);return}a()};d()}}}}()},d=window.CKEDITOR_GETURL;if(d){var g=b.getUrl;b.getUrl=function(a){return d.call(b,a)||g.call(b,a)}}return b}());
 /*jsl:end*/
 
 if ( CKEDITOR.loader )
diff --git a/core/ckeditor_base.js b/core/ckeditor_base.js
index 069793172a9..0f585f016af 100644
--- a/core/ckeditor_base.js
+++ b/core/ckeditor_base.js
@@ -9,9 +9,7 @@
  */
 
 // #### Compressed Code
-// Must be updated on changes in the script as well as updated in the ckeditor.js file.
-
-// window.CKEDITOR||(window.CKEDITOR=function(){var b={timestamp:"",version:"%VERSION%",revision:"%REV%",rnd:Math.floor(900*Math.random())+100,_:{pending:[]},status:"unloaded",basePath:function(){var a=window.CKEDITOR_BASEPATH||"";if(!a)for(var b=document.getElementsByTagName("script"),c=0;c<b.length;c++){var d=b[c].src.match(/(^|.*[\\\/])ckeditor(?:_basic)?(?:_source)?.js(?:\?.*)?$/i);if(d){a=d[1];break}}-1==a.indexOf(":/")&&"//"!=a.slice(0,2)&&(a=0===a.indexOf("/")?location.href.match(/^.*?:\/\/[^\/]*/)[0]+a:location.href.match(/^[^\?]*\/(?:)/)[0]+a);if(!a)throw'The CKEditor installation path could not be automatically detected. Please set the global variable "CKEDITOR_BASEPATH" before creating editor instances.';return a}(),getUrl:function(a){-1==a.indexOf(":/")&&0!==a.indexOf("/")&&(a=this.basePath+a);this.timestamp&&"/"!=a.charAt(a.length-1)&&!/[&?]t=/.test(a)&&(a+=(0<=a.indexOf("?")?"&":"?")+"t="+this.timestamp);return a},domReady:function(){function a(){try{document.addEventListener?(document.removeEventListener("DOMContentLoaded",a,!1),b()):document.attachEvent&&"complete"===document.readyState&&(document.detachEvent("onreadystatechange",a),b())}catch(d){}}function b(){for(var a;a=c.shift();)a()}var c=[];return function(b){c.push(b);"complete"===document.readyState&&setTimeout(a,1);if(1==c.length)if(document.addEventListener)document.addEventListener("DOMContentLoaded",a,!1),window.addEventListener("load",a,!1);else if(document.attachEvent){document.attachEvent("onreadystatechange",a);window.attachEvent("onload",a);b=!1;try{b=!window.frameElement}catch(e){}if(document.documentElement.doScroll&&b){var f=function(){try{document.documentElement.doScroll("left")}catch(b){setTimeout(f,1);return}a()};f()}}}}()},e=window.CKEDITOR_GETURL;if(e){var g=b.getUrl;b.getUrl=function(a){return e.call(b,a)||g.call(b,a)}}return b}());
+// Compressed code in ckeditor.js must be be updated on changes in the script.
 // The Closure Compiler online service should be used when updating this manually:
 // http://closure-compiler.appspot.com/
 
@@ -25,6 +23,8 @@ if ( !window.CKEDITOR ) {
 	 * @singleton
 	 */
 	window.CKEDITOR = ( function() {
+		var basePathSrcPattern = /(^|.*[\\\/])ckeditor\.js(?:\?.*|;.*)?$/i;
+
 		var CKEDITOR = {
 
 			/**
@@ -76,7 +76,8 @@ if ( !window.CKEDITOR ) {
 			 * @private
 			 */
 			_: {
-				pending: []
+				pending: [],
+				basePathSrcPattern: basePathSrcPattern
 			},
 
 			/**
@@ -111,9 +112,6 @@ if ( !window.CKEDITOR ) {
 			 * @property {String}
 			 */
 			basePath: ( function() {
-				// ATTENTION: fixes to this code must be ported to
-				// var basePath in "core/loader.js".
-
 				// Find out the editor directory path, based on its <script> tag.
 				var path = window.CKEDITOR_BASEPATH || '';
 
@@ -121,7 +119,7 @@ if ( !window.CKEDITOR ) {
 					var scripts = document.getElementsByTagName( 'script' );
 
 					for ( var i = 0; i < scripts.length; i++ ) {
-						var match = scripts[ i ].src.match( /(^|.*[\\\/])ckeditor(?:_basic)?(?:_source)?.js(?:\?.*)?$/i );
+						var match = scripts[ i ].src.match( basePathSrcPattern );
 
 						if ( match ) {
 							path = match[ 1 ];
@@ -312,4 +310,4 @@ if ( !window.CKEDITOR ) {
  * for details.
  */
 
-// PACKAGER_RENAME( CKEDITOR )
+// PACKAGER_RENAME( CKEDITOR )
\ No newline at end of file
diff --git a/core/loader.js b/core/loader.js
index 12207876833..b17e8962d61 100644
--- a/core/loader.js
+++ b/core/loader.js
@@ -76,39 +76,6 @@ if ( !CKEDITOR.loader ) {
 			'creators/inline': []
 		};
 
-		var basePath = ( function() {
-			// This is a copy of CKEDITOR.basePath, but requires the script having
-			// "_source/loader.js".
-			if ( CKEDITOR && CKEDITOR.basePath )
-				return CKEDITOR.basePath;
-
-			// Find out the editor directory path, based on its <script> tag.
-			var path = '';
-			var scripts = document.getElementsByTagName( 'script' );
-
-			for ( var i = 0; i < scripts.length; i++ ) {
-				var match = scripts[ i ].src.match( /(^|.*?[\\\/])(?:_source\/)?core\/loader.js(?:\?.*)?$/i );
-
-				if ( match ) {
-					path = match[ 1 ];
-					break;
-				}
-			}
-
-			// In IE (only) the script.src string is the raw valued entered in the
-			// HTML. Other browsers return the full resolved URL instead.
-			if ( path.indexOf( '://' ) == -1 ) {
-				// Absolute path.
-				if ( path.indexOf( '/' ) === 0 )
-					path = location.href.match( /^.*?:\/\/[^\/]*/ )[ 0 ] + path;
-				// Relative path.
-				else
-					path = location.href.match( /^[^\?]*\// )[ 0 ] + path;
-			}
-
-			return path;
-		} )();
-
 		var timestamp = ( CKEDITOR && CKEDITOR.timestamp ) || ( new Date() ).valueOf(); // %REMOVE_LINE%
 		/*																				// %REMOVE_LINE%
 		 * The production implementation contains a fixed timestamp						// %REMOVE_LINE%
@@ -120,7 +87,7 @@ if ( !CKEDITOR.loader ) {
 				if ( CKEDITOR && CKEDITOR.getUrl )
 					return CKEDITOR.getUrl( resource );
 
-				return basePath + resource + ( resource.indexOf( '?' ) >= 0 ? '&' : '?' ) + 't=' + timestamp;
+				return CKEDITOR.basePath + resource + ( resource.indexOf( '?' ) >= 0 ? '&' : '?' ) + 't=' + timestamp;
 			};
 
 		var pendingLoad = [];
diff --git a/tests/core/ckeditor/basepath.html b/tests/core/ckeditor/basepathglobal.html
similarity index 100%
rename from tests/core/ckeditor/basepath.html
rename to tests/core/ckeditor/basepathglobal.html
diff --git a/tests/core/ckeditor/basepath.js b/tests/core/ckeditor/basepathglobal.js
similarity index 100%
rename from tests/core/ckeditor/basepath.js
rename to tests/core/ckeditor/basepathglobal.js
diff --git a/tests/core/ckeditor/basepathproperty.html b/tests/core/ckeditor/basepathproperty.html
new file mode 100644
index 00000000000..5715b7a51c9
--- /dev/null
+++ b/tests/core/ckeditor/basepathproperty.html
@@ -0,0 +1,2 @@
+<iframe id="iframe-default-params"></iframe>
+<iframe id="iframe-semicolon-params"></iframe>
\ No newline at end of file
diff --git a/tests/core/ckeditor/basepathproperty.js b/tests/core/ckeditor/basepathproperty.js
new file mode 100644
index 00000000000..a4c5af02d8f
--- /dev/null
+++ b/tests/core/ckeditor/basepathproperty.js
@@ -0,0 +1,65 @@
+/* bender-tags: editor,unit */
+
+( function() {
+	'use strict';
+
+	bender.test( {
+		'test CKEDITOR.basePath when used src="ckeditor.js?foo&bar"': function() {
+			var iframe = CKEDITOR.document.getById( 'iframe-default-params' ),
+				doc = iframe.getFrameDocument();
+
+			iframe.on( 'load', function() {
+				resume( function() {
+					var iCKEDITOR = iframe.$.contentWindow.CKEDITOR;
+
+					assert.areSame( CKEDITOR.basePath, iCKEDITOR.basePath );
+				} );
+			} );
+
+			doc.$.open();
+			doc.$.write( '<script src="' + CKEDITOR.getUrl( 'ckeditor.js' ) + '?foo=1&bar=2"></scr' + 'ipt>' );
+			doc.$.close();
+
+			wait();
+		},
+
+		'test CKEDITOR.basePath ckeditor.js src pattern': function() {
+			var pattern = CKEDITOR._.basePathSrcPattern;
+
+			a( 'ckeditor.js' );
+			a( '/ckeditor.js' );
+			a( '\\ckeditor.js' );
+			a( '/ckeditor.js?foo=1#bar' );
+			a( 'CKEDITOR.JS' );
+			// #12215
+			a( '/ckeditor.js;id=foo-bar' );
+
+			function a( src ) {
+				assert.isMatching( pattern, src, src );
+			}
+		},
+
+		/*
+		#12215
+		Test impossible to perform with present Bender's capabilities.
+		'test CKEDITOR.basePath when used src="ckeditor.js;foo&bar"': function() {
+			var iframe = CKEDITOR.document.getById( 'iframe-semicolon-params' ),
+				doc = iframe.getFrameDocument();
+
+			iframe.on( 'load', function() {
+				resume( function() {
+					var iCKEDITOR = iframe.$.contentWindow.CKEDITOR;
+
+					assert.areSame( CKEDITOR.basePath, iCKEDITOR.basePath );
+				} );
+			} );
+
+			doc.$.open();
+			doc.$.write( '<script src="' + CKEDITOR.getUrl( 'ckeditor.js' ) + ';foo=1&bar=2"></scr' + 'ipt>' );
+			doc.$.close();
+
+			wait();
+		}
+		*/
+	} );
+} )();
\ No newline at end of file