The remote host is vulnerable to a flaw that allows for the bypassing of authentication.
The remote host is running a version of vBulletin, a forum application implemented in PHP, that is vulnerable to an unspecified remote vulnerability. It is reported that versions prior to 3.0.5 are prone to this issue. Additionally, versions of vBulletin prior to 3.0.5 are vulnerable to a content-parsing flaw within the forumdisplay.php script. An attacker exploiting this flaw would be able to run arbitrary commands on the remote web server.
Upgrade to vBulletin 3.0.5 or higher.