source: https://www.securityfocus.com/bid/9888/info

It has been reported that VBulletin is prone to a cross-site scripting vulnerability in the 'forumdisplay.php' script. This issue is reportedly due to a failure to sanitize user input and so allow for injection of HTML and script code that may facilitate cross-site scripting attacks. 

Successful exploitation of this issue may allow for theft of cookie-based authentication credentials or other attacks.

http://www.example.com/forumdisplay.php?f=[VID]&page=[INT]&sort=lastpost&order=[XSS]