diff --git a/Gemfile b/Gemfile
index 7362629bf..d36719329 100644
--- a/Gemfile
+++ b/Gemfile
@@ -85,10 +85,9 @@ gem 'nuntium_api', '~> 0.21'
 gem 'sentry-raven', '~> 2.13'
 
 # Assets
-gem 'execjs', '< 2.8.0' # 2.8 removed support for therubyracer
 gem 'gon', '~> 6.0'
 gem 'sass-rails', '~> 5.0', '< 5.0.8'
-gem 'therubyracer', '~> 0.12' # FIXME: deprecated for years
+gem 'mini_racer'
 gem 'turbolinks', '~> 2.5' # TODO: upgrade to '~> 5'
 gem 'uglifier', '~> 2.7'
 
diff --git a/Gemfile.lock b/Gemfile.lock
index 6a246628a..2904a888c 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -320,7 +320,7 @@ GEM
     leaflet-rails (0.7.7)
     letter_opener (1.8.0)
       launchy (>= 2.2, < 3)
-    libv8 (3.16.14.19)
+    libv8-node (15.14.0.1)
     listen (3.0.8)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
@@ -336,6 +336,8 @@ GEM
     mime-types (2.99.3)
     mini_mime (1.1.2)
     mini_portile2 (2.4.0)
+    mini_racer (0.4.0)
+      libv8-node (~> 15.14.0.0)
     minitest (5.15.0)
     multi_json (1.15.0)
     multi_test (0.1.2)
@@ -446,7 +448,6 @@ GEM
     recaptcha (4.9.0)
       json
     redis (3.3.5)
-    ref (2.0.0)
     request_store (1.5.1)
       rack (>= 1.4)
     responders (2.4.1)
@@ -537,9 +538,6 @@ GEM
       actionpack (>= 4.0)
       activesupport (>= 4.0)
       sprockets (>= 3.0.0)
-    therubyracer (0.12.3)
-      libv8 (~> 3.16.14.15)
-      ref
     thor (1.2.1)
     thread_safe (0.3.6)
     tilt (2.0.10)
@@ -601,7 +599,6 @@ DEPENDENCIES
   dropzonejs-rails (~> 0.8.4)
   elasticsearch (~> 1.0)
   encryptor (~> 1.3)
-  execjs (< 2.8.0)
   faker (< 1.9.2)
   ffaker (< 2.12.0)
   geojson_import!
@@ -619,6 +616,7 @@ DEPENDENCIES
   location_service!
   lodash-rails (~> 3.10.1)
   machinist (~> 2.0)
+  mini_racer
   mysql2 (~> 0.3)
   nokogiri (~> 1.6, < 1.10.0)
   nuntium_api (~> 0.21)
@@ -662,7 +660,6 @@ DEPENDENCIES
   spring-commands-rspec
   spring-watcher-listen (~> 2.0.0)
   sprockets-rails (< 3.3.0)
-  therubyracer (~> 0.12)
   timecop (~> 0.8)
   turbolinks (~> 2.5)
   uglifier (~> 2.7)
@@ -673,4 +670,4 @@ DEPENDENCIES
   wicked_pdf (~> 2.1)
 
 BUNDLED WITH
-   1.16.1
+   1.17.3
diff --git a/app/models/manifest_field_mapping.rb b/app/models/manifest_field_mapping.rb
index e48a16d12..c9891f75a 100644
--- a/app/models/manifest_field_mapping.rb
+++ b/app/models/manifest_field_mapping.rb
@@ -1,3 +1,5 @@
+require_relative "./xml_message_serializer"
+
 class ManifestFieldMapping
   include DateDistanceHelper
 
@@ -121,45 +123,35 @@ def check_op(node, name)
   end
 
   def run_script(script, data)
-    ctx = V8::Context.new
-    begin
-      ctx["message"] = data
+    ctx = MiniRacer::Context.new
 
-      if @device
-        ctx["device"] = script_device(@device)
-        if site = @device.site
-          ctx["site"] = script_site(site)
-        end
-        if location = site.try(&:location)
-          ctx["location"] = script_location(location)
-        end
+    if data.is_a?(Nokogiri::XML::Node)
+      ctx.eval "var message = #{data.cdx_serializable_hash.to_json};"
+      ctx.attach "message.xpath", ->(query) { data.xpath(query).cdx_serializable_hash }
+    else
+      ctx.eval "var message = #{data.to_json};"
+    end
+
+    if @device
+      ctx.eval "var device = #{script_device(@device).to_json};"
+
+      if site = @device.site
+        ctx.eval "var site = #{script_site(site).to_json};"
       end
+      if location = site.try(&:location)
+        ctx.eval "var location = #{script_location(location).to_json};"
+      end
+    end
 
-      result = ctx.eval(script)
-      result = to_ruby(result)
-      result
-    rescue V8::Error => e
+    begin
+      ctx.eval(script)
+    rescue MiniRacer::Error => e
       raise ManifestParsingError.script_error(@field.target_field, e.message)
     ensure
       ctx.dispose
     end
   end
 
-  def to_ruby(v8_object)
-    case v8_object
-    when V8::Array
-      array = v8_object.to_a
-      array.map! { |elem| to_ruby(elem) }
-    when V8::Object
-      hash = v8_object.to_h
-      hash.each do |key, value|
-        hash[key] = to_ruby(value)
-      end
-    else
-      v8_object
-    end
-  end
-
   def script_device(device)
     {
       uuid: device.uuid,
diff --git a/app/models/xml_message_serializer.rb b/app/models/xml_message_serializer.rb
new file mode 100644
index 000000000..caf646e17
--- /dev/null
+++ b/app/models/xml_message_serializer.rb
@@ -0,0 +1,62 @@
+# Custom serialization of Nokogiri nodes to trivial data structures, that are
+# easy to serialize to another language, such as JavaScript, as used in
+# `ManifestFieldMapping#run_script` for example.
+
+class Nokogiri::XML::Attr
+  def cdx_name_with_nsprefix
+    if namespace
+      "#{namespace.prefix}:#{name}"
+    else
+      name
+    end
+  end
+
+  def cdx_serializable_hash
+    { "name" => cdx_name_with_nsprefix, "value" => value }
+  end
+end
+
+class Nokogiri::XML::CDATA
+  def cdx_serializable_hash
+    content
+  end
+end
+
+class Nokogiri::XML::Document
+  def cdx_serializable_hash
+    root.cdx_serializable_hash
+  end
+end
+
+class Nokogiri::XML::Element
+  def cdx_serializable_hash
+    hsh = { "name" => name }
+
+    unless attribute_nodes.empty?
+      hsh["attributes"] = attribute_nodes
+        .each_with_object({}) { |attr, h| h[attr.cdx_name_with_nsprefix] = attr.value }
+    end
+
+    unless children.empty?
+      hsh["children"] = children
+        .map { |node| node.cdx_serializable_hash if node.respond_to?(:cdx_serializable_hash) }
+        .compact
+    end
+
+    hsh
+  end
+end
+
+class Nokogiri::XML::NodeSet
+  def cdx_serializable_hash
+    to_a
+      .map { |node| node.cdx_serializable_hash if node.respond_to?(:cdx_serializable_hash) }
+      .compact
+  end
+end
+
+class Nokogiri::XML::Text
+  def cdx_serializable_hash
+    content
+  end
+end
diff --git a/spec/models/manifest_operations_spec.rb b/spec/models/manifest_operations_spec.rb
index f9412b5f9..c38b68092 100644
--- a/spec/models/manifest_operations_spec.rb
+++ b/spec/models/manifest_operations_spec.rb
@@ -122,10 +122,26 @@
       {"sample" => {"custom" => {"fields" => "#{loc.name},#{loc.lat.to_i},#{loc.lng.to_i}"}, "pii" => {}, "core" => {}}}, device
     end
 
-    it "loads xml in javascript" do
+    it "loads xml in javascript (serialized hash)" do
       assert_manifest_application %(
         {
-          "patient.name": {"script": "message.xpath('Patient/@name').first().value"}
+          "patient.name": {"script": "message.children.find(function (node) { return node.name === 'Patient' }).attributes.name"}
+        }
+      ), %(
+        {
+        }
+      ), {xml: %(
+        <Message>
+          <Patient name="Socrates" age="27"/>
+        </Message>
+      )},
+      "patient" => {"custom" => {}, "pii" => {"name" => "Socrates"}, "core" => {}}
+    end
+
+    it "loads xml in javascript (xpath)" do
+      assert_manifest_application %(
+        {
+          "patient.name": {"script": "message.xpath('Patient/@name')[0].value"}
         }
       ), %(
         {