NOTE: this issue has been disputed by the vendor. Cross-site scripting (XSS) vulnerability in register.php for unknown versions of vBulletin allows remote attackers to inject arbitrary HTML or web script via the reg_site (or possibly regsite) parameter. NOTE: the vendor has disputed this issue, saying "There is no hidden field called 'reg_site', nor any $reg_site variable anywhere in the vBulletin 2 or vBulletin 3 source code or templates, nor has it ever existed. We can only assume that this vulnerability was found in a site running code modified from that supplied by Jelsoft.