diff --git a/customize.dist/translations/messages.fr.js b/customize.dist/translations/messages.fr.js
index e719a44d9..24fff7a37 100644
--- a/customize.dist/translations/messages.fr.js
+++ b/customize.dist/translations/messages.fr.js
@@ -436,11 +436,10 @@ define(function () {
     ].join('');
 
     out.codeInitialState = [
-        '/*\n',
-        '   Voici l\'éditeur de code collaboratif et Zero Knowledge de CryptPad.\n',
-        '   Ce que vous tapez ici est chiffré de manière que seules les personnes avec le lien peuvent y accéder.\n',
-        '   Vous pouvez choisir le langage de programmation pour la coloration syntaxique, ainsi que le thème de couleurs, dans le coin supérieur droit.\n',
-        '*/'
+        '# Éditeur de code collaboratif et Zero Knowledge de CryptPad\n',
+        '\n',
+        '* Ce que vous tapez ici est chiffré de manière que seules les personnes avec le lien peuvent y accéder.\n',
+        '* Vous pouvez choisir le langage de programmation pour la coloration syntaxique, ainsi que le thème de couleurs, dans le coin supérieur droit.'
     ].join('');
 
     out.slideInitialState = [
diff --git a/customize.dist/translations/messages.js b/customize.dist/translations/messages.js
index 10efcb2df..c357cb557 100644
--- a/customize.dist/translations/messages.js
+++ b/customize.dist/translations/messages.js
@@ -450,11 +450,10 @@ define(function () {
     ].join('');
 
     out.codeInitialState = [
-        '/*\n',
-        '   This is the CryptPad Zero Knowledge collaborative code editor.\n',
-        '   What you type here is encrypted so only people who have the link can access it.\n',
-        '   You can choose the programming language to highlight and the UI color scheme in the upper right.\n',
-        '*/'
+        '# CryptPad\'s Zero Knowledge collaborative code editor\n',
+        '\n',
+        '* What you type here is encrypted so only people who have the link can access it.\n',
+        '*  You can choose the programming language to highlight and the UI color scheme in the upper right.'
     ].join('');
 
     out.slideInitialState = [
diff --git a/www/common/diffMarked.js b/www/common/diffMarked.js
new file mode 100644
index 000000000..b3cc5fe1e
--- /dev/null
+++ b/www/common/diffMarked.js
@@ -0,0 +1,109 @@
+define([
+    'jquery',
+    '/bower_components/marked/marked.min.js',
+    '/bower_components/diff-dom/diffDOM.js'
+],function ($, Marked) {
+    var DiffMd = {}
+
+    var DiffDOM = window.diffDOM;
+    var renderer = DiffMd.renderer = new Marked.Renderer();
+
+    Marked.setOptions({
+        renderer: renderer
+    });
+
+    DiffMd.render = function (md) {
+        return Marked(md);
+    };
+
+    var forbiddenTags = [
+        'SCRIPT',
+        'IFRAME',
+        'OBJECT',
+        'APPLET',
+        'VIDEO',
+        'AUDIO',
+    ];
+    var unsafeTag = function (info) {
+        if (['addAttribute', 'modifyAttribute'].indexOf(info.diff.action) !== -1) {
+            if (/^on/.test(info.diff.name)) {
+                console.log("Rejecting forbidden element attribute with name", info.diff.name);
+                return true;
+            }
+        }
+        if (['addElement', 'replaceElement'].indexOf(info.diff.action) !== -1) {
+            var msg = "Rejecting forbidden tag of type (%s)";
+            if (info.diff.element && forbiddenTags.indexOf(info.diff.element.nodeName) !== -1) {
+                console.log(msg, info.diff.element.nodeName);
+                return true;
+            } else if (info.diff.newValue && forbiddenTags.indexOf(info.diff.newValue.nodeName) !== -1) {
+                console.log("Replacing restricted element type (%s) with PRE", info.diff.newValue.nodeName);
+                info.diff.newValue.nodeName = 'PRE';
+            }
+        }
+    };
+
+    var slice = function (coll) {
+        return Array.prototype.slice.call(coll);
+    };
+
+    /*  remove listeners from the DOM */
+    var removeListeners = function (root) {
+        slice(root.attributes).map(function (attr) {
+            if (/^on/.test(attr.name)) {
+                root.attributes.removeNamedItem(attr.name);
+            }
+        });
+        // all the way down
+        slice(root.children).forEach(removeListeners);
+    };
+
+    var domFromHTML = function (html) {
+        var Dom = new DOMParser().parseFromString(html, "text/html");
+        removeListeners(Dom.body);
+        return Dom;
+    };
+
+    var DD = new DiffDOM({
+        preDiffApply: function (info) {
+            if (unsafeTag(info)) { return true; }
+        }
+    });
+
+    var makeDiff = function (A, B, id) {
+        var Err;
+        var Els = [A, B].map(function (frag) {
+            if (typeof(frag) === 'object') {
+                if (!frag || (frag && !frag.body)) {
+                    Err = "No body";
+                    return;
+                }
+                var els = frag.body.querySelectorAll('#'+id);
+                if (els.length) {
+                    return els[0];
+                }
+            }
+            Err = 'No candidate found';
+        });
+        if (Err) { return Err; }
+        var patch = DD.diff(Els[0], Els[1]);
+        return patch;
+    };
+
+    var apply = DiffMd.apply = function (newHtml, $content) {
+        var id = $content.attr('id');
+        if (!id) { throw new Error("The element must have a valid id"); }
+        var $div = $('<div>', {id: id}).append(newHtml);
+        var Dom = domFromHTML($('<div>').append($div).html());
+        var oldDom = domFromHTML($content[0].outerHTML);
+        var patch = makeDiff(oldDom, Dom, id);
+        if (typeof(patch) === 'string') {
+            throw new Error(patch);
+        } else {
+            DD.apply($content[0], patch);
+        }
+    };
+
+    return DiffMd;
+});
+