diff --git a/www/debug/main.js b/www/debug/main.js
index 6f855e1db..124ea39f9 100644
--- a/www/debug/main.js
+++ b/www/debug/main.js
@@ -13,6 +13,9 @@ define([
     '/common/common-interface.js',
 ], function (nThen, ApiConfig, $, RequireConfig, SFCommonO,
     Cryptpad, Util, Hash, Realtime, Constants, UI) {
+    if (window.top !== window) {
+        return void window.alert(`If you are seeing this message then somebody might be trying to compromise your CryptPad account. Please contact the CryptPad development team.`);
+    }
 
     window.Cryptpad = {
         Common: Cryptpad,
diff --git a/www/login/main.js b/www/login/main.js
index df0be1733..1a27343fc 100644
--- a/www/login/main.js
+++ b/www/login/main.js
@@ -10,6 +10,7 @@ define([
 
     'css!/bower_components/components-font-awesome/css/font-awesome.min.css',
 ], function ($, Cryptpad, Login, UI, Realtime, Feedback, LocalStore /*, Test */) {
+    if (window.top !== window) { return; }
     $(function () {
         var $checkImport = $('#import-recent');
         if (LocalStore.isLoggedIn()) {
diff --git a/www/register/main.js b/www/register/main.js
index 301306f70..8edbaab92 100644
--- a/www/register/main.js
+++ b/www/register/main.js
@@ -14,6 +14,7 @@ define([
 
     'css!/bower_components/components-font-awesome/css/font-awesome.min.css',
 ], function ($, Login, Cryptpad, /*Test,*/ Cred, UI, Util, Realtime, Constants, Feedback, LocalStore, h) {
+    if (window.top !== window) { return; }
     var Messages = Cryptpad.Messages;
     $(function () {
         if (LocalStore.isLoggedIn()) {