PHP-Post 0.21 and 1.0, and possibly earlier versions, when auto-login is enabled, allows remote attackers to bypass security restrictions and obtain administrative privileges by modifying the logincookie[user] setting in the login cookie.
https://www.exploit-db.com/exploits/2036
https://exchange.xforce.ibmcloud.com/vulnerabilities/27862
http://www.vupen.com/english/advisories/2006/2877
http://www.securityfocus.com/archive/1/440419/100/0/threaded