Directory traversal vulnerability in clientarea.php in WHMCompleteSolution (WHMCS) 3.x.x allows remote attackers to read arbitrary files via an invalid action and a ../ (dot dot slash) in the templatefile parameter.
Improper Limitation of a Pathname to a Restricted Directory The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.