diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 7fee212d2a6..2da42748a20 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -243,12 +243,20 @@ class ApplicationController < ActionController::Base
     end
 
     def custom_html_json
-      MultiJson.dump({
+      data = {
         top: SiteContent.content_for(:top),
         bottom: SiteContent.content_for(:bottom)
-      }.merge(
-        (SiteSetting.tos_accept_required && !current_user) ? {tos_signup_form_message: SiteContent.content_for(:tos_signup_form_message)} : {}
-      ))
+      }
+
+      if SiteSetting.tos_accept_required && !current_user
+        data[:tos_signup_form_message] = SiteContent.content_for(:tos_signup_form_message)
+      end
+
+      if DiscoursePluginRegistry.custom_html
+        data.merge! DiscoursePluginRegistry.custom_html
+      end
+
+      MultiJson.dump(data)
     end
 
     def render_json_error(obj)
diff --git a/lib/discourse_plugin_registry.rb b/lib/discourse_plugin_registry.rb
index 1a32e478e00..bfb8f67de69 100644
--- a/lib/discourse_plugin_registry.rb
+++ b/lib/discourse_plugin_registry.rb
@@ -12,6 +12,7 @@ class DiscoursePluginRegistry
     attr_accessor :desktop_stylesheets
     attr_accessor :sass_variables
     attr_accessor :handlebars
+    attr_accessor :custom_html
 
     # Default accessor values
     def javascripts
diff --git a/lib/plugin/instance.rb b/lib/plugin/instance.rb
index e8e5ccd5145..88498a5e149 100644
--- a/lib/plugin/instance.rb
+++ b/lib/plugin/instance.rb
@@ -108,6 +108,11 @@ class Plugin::Instance
     @javascripts << js
   end
 
+  def register_custom_html(hash)
+    DiscoursePluginRegistry.custom_html ||= {}
+    DiscoursePluginRegistry.custom_html.merge!(hash)
+  end
+
   def register_asset(file, opts=nil)
     full_path = File.dirname(path) << "/assets/" << file
     assets << [full_path, opts]