Session fixation vulnerability in Simple Machines Forum (SMF) 1.1.2 and earlier allows remote attackers to hijack web sessions by setting the PHPSESSID parameter.
http://www.securityfocus.com/bid/24482
http://www.securityfocus.com/archive/1/471414/100/0/threaded
http://www.securityfocus.com/archive/1/467748/100/0/threaded
http://www.majorsecurity.de/index_2.php?major_rls=major_rls47
http://securityreason.com/securityalert/2676