ELEX WordPress HelpDesk & Customer Ticketing System <= 3.3.9 - Unauthenticated PHP Object Injection to Remote Code Execution via 'form' Parameter

The ELEX WordPress HelpDesk & Customer Ticketing System plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 3.3.9 via the 'form (specifically the attacker-controlled ticket_label field inside the url-encoded form string)' parameter parameter. This is due to missing server-side authentication and the absence of a class allowlist on deserialization, with the only guard being a nonce publicly emitted on any page carrying the [wsdesk_support] shortcode. This makes it possible for unauthenticated attackers to execute code on the server. A successful exploit requires a single anonymous GET to any public page carrying the [wsdesk_support] shortcode to harvest the publicly emitted wsdesk_nonce value, after which a single unauthenticated POST completes the attack.