Geeklog 1.3 allows remote attackers to hijack user accounts, including the administrator account, by modifying the UID of a user's permanent cookie to the target account.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2002-0097
http://www.securityfocus.com/bid/3844
http://www.iss.net/security_center/static/7869.php