WHMCS has released new patches for the 4.5, 5.0, 5.1, and 5.2 minor releases. These updates provide targeted changes to address security concerns with the WHMCS product. You are highly encouraged to update immediately.
WHMCS has rated these updates as including critical or important security impacts. Information on security ratings is available at http://docs.whmcs.com/Security_Levels.
The following full-release versions of WHMCS have been published and address all known vulnerabilities:
Read more @ http://blog.whmcs.com/?t=76310