PHPX 2.0 through 3.2.4 allows remote attackers to gain access to other accounts by modifying the cookie's PXL variable to reference another userID.
https://exchange.xforce.ibmcloud.com/vulnerabilities/15512
https://exchange.xforce.ibmcloud.com/vulnerabilities/15052
http://secunia.com/advisories/10797/
http://marc.info/?l=bugtraq&m=107586932324901&w=2
http://archives.neohapsis.com/archives/bugtraq/2004-03/0154.html