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Advisory 11/2006: Serendipity Weblog XSS Vulnerabilities
From: Stefan Esser <sesser () hardened-php net>
Date: Thu, 19 Oct 2006 17:55:28 +0200

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                        Hardened-PHP Project
                        www.hardened-php.net

                      -= Security  Advisory =-


     Advisory: Serendipity Weblog XSS Vulnerabilities
 Release Date: 2006/10/19
Last Modified: 2006/10/19
       Author: Stefan Esser [sesser () hardened-php net]

  Application: Serendipity <= 1.0.1
     Severity: Multiple XSS vulnerabilities within the administration
               interface allow Cross Site Scripting attacks against
               the blog admin
         Risk: Critical
Vendor Status: Vendor has a released an updated version
   References: http://www.hardened-php.net/advisory_112006.136.html


Overview:

   Quote from http://www.s9y.org
   "Serendipity is a PHP-powered weblog application which gives the 
    user an easy way to maintain an online diary, weblog or even a 
    complete homepage. While the default package is designed for 
    the casual blogger, Serendipity offers a flexible, expandable 
    and easy-to-use framework with the power for professional 
    applications."

   During an quick audit of Serendipity it was discovered that 
   multiple XSS vulnerabilities exist in the administration area.
   Because of this vulnerabilities it is possible for an attacker
   that tricks an admin into visiting a special prepared website
   to perform any administrative action in the blog. This includes
   posting entries or adding additional admin users.
   
   Tricking a blog admin to visit a certain website is usually as
   simple as mentioning an URL in the comments of his blog.
   

Details:

   Serendipity failed to correctly sanitize user input on the 
   media manager administration page. The content of GET variables
   were written into JavaScript strings. By using standard string 
   evasion techniques it was possible to execute arbitrary 
   JavaScript.
   
   Additionally Serendipity dynamically created a HTML form on
   the media manager administration page that contained all
   variables found in the URL as hidden fields. While the variable
   values were correctly escaped it was possible to break out
   by specifying strange variable names.
   

Proof of Concept:

   The Hardened-PHP Project is not going to release exploits for
   this vulnerability to the public.


Disclosure Timeline:

   05. October 2006 - Contacted Serendipity developers by email
   18. October 2006 - Updated Serendipity was released
   19. October 2006 - Public Disclosure


Recommendation:

   It is strongly recommended to upgrade to the newest version of
   Serendipity 1.0.2 which you can download at:

   http://prdownloads.sourceforge.net/php-blog/serendipity-1.0.2.tar.gz?download
   

GPG-Key:

   http://www.hardened-php.net/hardened-php-signature-key.asc

   pub  1024D/0A864AA1 2004-04-17 Hardened-PHP Signature Key
   Key fingerprint = 066F A6D0 E57E 9936 9082  7E52 4439 14CC 0A86 4AA1


Copyright 2006 Stefan Esser. All rights reserved.

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