Drupal CKEditor 3.0 - 3.6.2 - Persistent EventHandler XSS Jan 18 2012 07:35PM
InterN0T Advisories (advisories intern0t net)
# Exploit Title: Drupal CKEditor 3.0 - 3.6.2 - Persistent EventHandler XSS

# Google Dork: "inurl:"sites/all/modules/ckeditor" -drupalcode.org"

# Google Results: Approximately 379.000 results

# Date: 18th January 2012

# Author: MaXe @InterN0T (Found in a private Hatforce.com Penetration


# Software Link: http://ckeditor.com/ & http://drupal.org/node/1332022

# Version: 3.0 - Current 3.6.2 (Drupal module: 6.x-1.8)

# Screenshot: http://i.imgur.com/8TP6w.png

# Tested on: Windows + FireFox 8.0 & Internet Explorer 8.0

Drupal CKEditor - Persistent / Stored Cross-Site Scripting

Versions Affected: 3.0 - 3.6.2 (Developers confirm all versions since 3.0

are affected.)


CKEditor is a text editor to be used inside web pages. It's a WYSIWYG

editor, which

means that the text being edited on it looks as similar as possible to the

results users

have when publishing it. It brings to the web common editing features

found on desktop

editing applications like Microsoft Word and OpenOffice.

External Links:



Credits: MaXe (@InterN0T) - Hatforce.com

-:: The Advisory ::-

CKEditor is prone to Persistent Cross-Site Scripting within the actual

editor, as

it is possible for an attacker could maliciously inject eventhandlers

serving java-

script code in preview / editing in html mode.

If an attacker injects an eventhandler into an image, such as


then the javascript will execute, even if the data is saved and previewed

in editing

mode later on. (The XSS will only executing during preview / editing in

html mode.)

If an administrator tries to edit the comment afterward, or is logged in

and browses

to the edit page of the malicious comment, then he or she will execute the


allowing attacker controlled code to run in the context of the browser.

Proof of Concept:

Switching to "raw mode" in CKEditor and then writing:

<p><img onload="alert(0);"



Will become this when it is saved:

<p><img data-cke-pa-onload="alert(0);"



If one searches for alert(0); in Firebug after the code has been injected

and executed, the location of the script will be:


Where $full_url_to_script is e.g. the following:


The content of this script is:

function onload(event) {



As there is a HTML filter in Drupal, it does not matter whether the <img>

tag is allowed in this case, as it was possible to execute the eventhandler

either way. (And even store the data.)

-:: Solution ::-

There is currently no solution, as it's not a critical bug according to

developers. See comments at: https://dev.ckeditor.com/ticket/8630 for more


At the same page there is an unofficial patch that should fix the problem,

however it seems that it will not fix the bug in Chrome.

Disclosure Information:

6th December 2011 - Vulnerability found during a private

http://www.hatforce.com Penetration Test

7th December 2011 - Researched and confirmed the vulnerability

4th January 2012 - Reported to Drupal and CKEditor via

http://drupal.org/project/ckeditor and http://dev.ckeditor.com/ and


18th January 2012 - Developers of CKEditor has been contacted several

times, nothing has happened in two weeks and the advisory has been

available to the public via bugtrackers. Vulnerability released to the

general public.

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