Insufficient ownership check in clientarea.php allows an authenticated client area user to submit requests using another user’s addonId without any ownership validation leading to unauthorized access to the victim's account.

SQL injection vulnerability in submitticket.php in WHMCompleteSolution (WHMCS) 4.2 allows remote attackers to execute arbitrary SQL commands via the deptid parameter.

SQL injection vulnerability in the gpLoadUserFromHash function in functionshash.php in the Group Pay module 1.5 and earlier for WHMCS allows remote attackers to execute arbitrary SQL commands via the hash parameter.

functions.php in WHMCompleteSolution (WHMCS) 4.0.x through 5.0.x allows remote attackers to trigger arbitrary code execution in the Smarty templating system by submitting a crafted ticket, related to improper handling of characters in the subject field.

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.

Multiple directory traversal vulnerabilities in WHMCompleteSolution (WHMCS) 3.x and 4.x allow remote attackers to read arbitrary files via the templatefile parameter to (1) submitticket.php and (2) downloads.php, and (3) the report parameter to admin/reports.php.

DISPUTED submitticket.php in WHMCompleteSolution (WHMCS) 5.03 allows remote attackers to inject arbitrary code into a subject field via crafted ticket data, a different vulnerability than CVE-2011-5061. NOTE: the vendor disputes this issue, noting that some of the details overlap CVE-2011-5061, but that it "says it affects V5.0.3, and the submitticket.php file, both of which are wrong."