The WHMCS Bridge WordPress plugin is vulnerable to Stored Cross-Site Scripting via the cc_whmcs_bridge_url parameter found in the ~/whmcs-bridge/bridge_cp.php file which allows attackers to inject arbitrary web scripts in versions up to and including 6.1. Due to missing authorization checks on the cc_whmcs_bridge_add_admin function low-level authenticated users such as subscribers can exploit this vulnerability.