diff --git a/wagtail/wagtailadmin/static/wagtailadmin/js/userbar.js b/wagtail/wagtailadmin/static/wagtailadmin/js/userbar.js
index 75f832c39..443a718ed 100644
--- a/wagtail/wagtailadmin/static/wagtailadmin/js/userbar.js
+++ b/wagtail/wagtailadmin/static/wagtailadmin/js/userbar.js
@@ -1,4 +1,4 @@
-/* No jQuery to speed up loading */
+"use strict";
 document.addEventListener('DOMContentLoaded', function(){
     var body = document.querySelectorAll('body')[0];
     var nav = document.querySelectorAll('nav')[0];
diff --git a/wagtail/wagtailadmin/static/wagtailadmin/js/userbar_embed.js b/wagtail/wagtailadmin/static/wagtailadmin/js/userbar_embed.js
index f2ba2016b..2bc6bcb17 100644
--- a/wagtail/wagtailadmin/static/wagtailadmin/js/userbar_embed.js
+++ b/wagtail/wagtailadmin/static/wagtailadmin/js/userbar_embed.js
@@ -1,19 +1,25 @@
 (function(w,d){
-    var l, f, h, frame_height;
+    "use strict";
+
+    var l, f, t, frame_height;
+
+    function callback(e){
+        var h;
+        if(e.origin !== w.wagtail.userbar.origin){return;};
+
+        // Get the height from the passed data.
+        try{
+            h = Number(e.data.replace( /.*fh=(\d+)(?:&|$)/, '$1' ) );
+            if (!isNaN( h ) && h > 0 && h !== frame_height) {
+                f.style.opacity = 1;
+                f.style.height = h + "px";
+            }
+        } catch(e){}
+    }
 
     if(!w.wagtail) return;
 
     if(w.postMessage){
-        function callback(e){
-            f.style.opacity=1;
-
-            // Get the height from the passed data.
-            var h = Number(e.data.replace( /.*fh=(\d+)(?:&|$)/, '$1' ) );
-            if (!isNaN( h ) && h > 0 && h !== frame_height) {
-                f.style.height = h + "px";
-            }
-        }
-
         if (w.addEventListener) {
             w.addEventListener('message', callback, false);
         } else {
@@ -25,12 +31,12 @@
     l.rel = 'stylesheet';
     l.href = w.wagtail.static_root + 'scss/userbar_embed.css';
 
-    f = d.createElement('iframe'); 
+    f = d.createElement('iframe');
     f.id = 'wagtail-userbar'; 
     f.frameborder = '0'; 
     f.allowtransparency = 'true'; 
     f.scrolling = 'no';
-    f.src = w.wagtail.userbar_src;
+    f.src = w.wagtail.userbar.src;
 
     // if postMessage is supported, hide iframe till it is loaded
     if(w.postMessage){
diff --git a/wagtail/wagtailadmin/templates/wagtailadmin/userbar/frame.html b/wagtail/wagtailadmin/templates/wagtailadmin/userbar/frame.html
index c7cfd784b..c9a5588b3 100644
--- a/wagtail/wagtailadmin/templates/wagtailadmin/userbar/frame.html
+++ b/wagtail/wagtailadmin/templates/wagtailadmin/userbar/frame.html
@@ -3,7 +3,10 @@
 <script type="text/javascript">
     var wagtail = wagtail || {};
     wagtail.static_root = '{% static "wagtailadmin/" %}';
-    wagtail.userbar_src = '{% if revision_id %}{% url "wagtailadmin_userbar_moderation" revision_id %}{% else %}{% url "wagtailadmin_userbar_frontend" page.self.id %}{% endif %}';
+    wagtail.userbar = {
+        src: '{% if revision_id %}{% url "wagtailadmin_userbar_moderation" revision_id %}{% else %}{% url "wagtailadmin_userbar_frontend" page.self.id %}{% endif %}',
+        origin:'{% if request.is_secure %}https{% else %}http{% endif %}://{{ request.get_host }}'
+    };
     (function(d) {
         var u = d.createElement('script'); u.type = 'text/javascript'; u.async = true;
         u.src = '{% static "wagtailadmin/js/userbar_embed.js" %}';
diff --git a/wagtail/wagtailadmin/views/userbar.py b/wagtail/wagtailadmin/views/userbar.py
index 9d15dfe45..7034baafc 100644
--- a/wagtail/wagtailadmin/views/userbar.py
+++ b/wagtail/wagtailadmin/views/userbar.py
@@ -18,6 +18,7 @@ def render_edit_frame(request, context):
 
     # Render the frame to contain the userbar items
     return render_to_string('wagtailadmin/userbar/frame.html', {
+        'request': request,
         'page': context,
         'revision_id': revision_id
     })