WHMCS has released a new update for all supported versions of WHMCS. These updates contain changes that address security concerns within the WHMCS product.
We recommend you update your WHMCS installation(s) as soon as possible.
WHMCS has rated this update as having an important security impact. Information on security ratings can be found at http://docs.whmcs.com/Security_Levels
Please update your installation to the one of the following versions:
Patches - What is a Patch?
Read more @ http://blog.whmcs.com/?t=84387