login.php in ACal Calendar Project 2.2.5 allows remote attackers to bypass authentication by setting the ACalAuthenticate cookie variable to "inside".
https://exchange.xforce.ibmcloud.com/vulnerabilities/24104
http://www.vupen.com/english/advisories/2006/0152
http://www.securityfocus.com/archive/1/421744/100/0/threaded
http://securityreason.com/securityalert/343