Open redirect vulnerability in forum/login.php in vBulletin 4.1.3 and earlier allows remote attackers to redirect users to arbitrary web sites and conduct phishing attacks via the url parameter in a lostpw action.
vBulletin 3.x.x and 4.2.x through 4.2.5 has an open redirect via the redirector.php url parameter.
vBulletin 5.4.3 has an Open Redirect.