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                        Hardened-PHP Project
                        www.hardened-php.net

                      -= Security  Advisory =-


     Advisory: WordPress CSRF Protection XSS Vulnerability
 Release Date: 2007/01/05
Last Modified: 2007/01/05
       Author: Stefan Esser [sesser@hardened-php.net]

  Application: WordPress <= 2.0.5
     Severity: The CSRF protection of WordPress's administration
               interface is vulnerable to an XSS vulnerability
               which might result in a compromise of the admin
               account and the execution of arbitrary PHP code
               on the server
         Risk: Critical
Vendor Status: Vendor has released WordPress 2.0.6 which fixes this issue
   References: https://www.hardened-php.net/advisory_012007.140.html


Overview:

   Quote from https://www.wordpress.org
   "WordPress was born out of a desire for an elegant, well-
    architectured personal publishing system built on PHP and MySQL 
    and licensed under the GPL. It is the official successor of 
    b2/cafelog. WordPress is fresh software, but its roots and 
    development go back to 2001. It is a mature and stable product. 
    We hope by focusing on user experience and web standards we can 
    create a tool different from anything else out there."

   While testing WordPress it was discovered that there is a XSS
   vulnerability in the CSRF protection of WordPress's administration
   interface. This might result in a compromise of the admin account
   and might result in the execution of arbitrary PHP code.


Details:

   The administration interface within WordPress comes with a token
   based CSRF protection. When a request is received with an invalid
   token it is not discarded like in many similar applications, but
   a warning screen is returned that asks the admin to verify the
   action by clicking on a link (that contains a valid token).
   
   Unfortunately there was a bug in the way the request information
   (URL variables) was put into the new link. Due to this fault it
   was possible to break out of the HTML string context by embedding
   quotes and HTML tags into the names of URL variables. 
   
   Due to this is is possible to launch XSS attacks against admin
   users currently logged into their WordPress and perform all possible
   administrative actions (or simply steal the login cookie). 
   Depending on the file permissions on the server (for example a 
   writeable wp-config.php or template file) this can also be 
   exploited to execute arbitrary PHP code.


Proof of Concept:

   The Hardened-PHP Project is not going to release a proof of concept 
   exploit for this vulnerability.


Disclosure Timeline:

   14. November 2006  - Notified security@wordpress.org
   05. January 2007   - WordPress 2.0.6 release
   05. January 2007   - Public Disclosure


Recommendation:

   We strongly recommend to upgrade to WordPress 2.0.6 which also
   fixes several other security vulnerabilities not covered by this
   advisory.
   
   https://wordpress.org/download/


GPG-Key:

   https://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 2007 Stefan Esser. All rights reserved.

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