Drupal Module CKEditor 3.0 < 3.6.2 - Persistent EventHandler Cross-Site Scripting
# 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 Test) # Software Link: http://ckeditor.com/ & http://drupal.org/node/1332022 # Version: 3.0 - Current 3.6.2 (Drupal module: 6.x-1.8) # Screenshot: If attached, see image file. # 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.) Info: 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: http://ckeditor.com/ http://drupal.org/node/1332022 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 "onload='alert(0);'", 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 javascript, 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);" src="http://1.images.napster.com/mp3s/2348/resources/324/363/files/324363272.jpg" /></p> Will become this when it is saved: <p><img data-cke-pa-onload="alert(0);" src="http://1.images.napster.com/mp3s/2348/resources/324/363/files/324363272.jpg" data-cke-saved-src="http://1.images.napster.com/mp3s/2348/resources/324/363/files/324363272.jpg"></p> If one searches for alert(0); in Firebug after the code has been injected and executed, the location of the script will be: $full_url_to_script/event/seq/4/onload Where $full_url_to_script is e.g. the following: http://localhost/drupal/drupal-6.22/?q=comment/edit/3/event/seq/4/onload The content of this script is: function onload(event) { alert(0); } 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 information. 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 http://cksource.com/contact 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. |