index.php in Jelsoft vBulletin does not properly initialize a PHP variable that is used to store template information, which allows remote attackers to execute arbitrary PHP code via special characters in the templatecache parameter.
https://exchange.xforce.ibmcloud.com/vulnerabilities/6237
http://www.vbulletin.com/forum/showthread.php?s=b20af207b5b908ecf7a4ecf56fbe3cd3&threadid=10839