A security issue has been reported to us that affects the versions of vBulletin listed here: 5.0.0, 5.0.1, 5.0.2, 5.0.3, 5.0.4, 5.0.5, 5.1.0, 5.1.1, and 5.1.2 We have released security patches to account for this vulnerability. The patch resolves a potential Cross-Site Forgery Request in the authorization system. It is recommended that all users install the patch provided for their version as soon as possible.
You can download the patch for your version here: http://members.vbulletin.com/patches.php
As part of our maintenance of Cloud Sites, we have applied the patch to those sites. If necessary, we will contact Cloud Customers with further information.
The current vBulletin 5.1.3 Alpha will include this fix on its next release...