source: http://www.securityfocus.com/bid/16178/info

427BB is prone to an authentication bypass vulnerability. This issue is due to a failure in the application to properly validate user-supplied data.

An attacker can exploit this issue to bypass the authentication mechanism and gain access to the affected application as an administrative user. This may facilitate a compromise of the underlying system; other attacks are also possible.

This issue affects version 2.2 and 2.2.1; other versions may also be vulnerable. 

The following demonstrates cookie-data sufficient to exploit this issue:
username=admin;
authenticated=1;
usertype=admin; 