The Paytium: Mollie payment forms & donations plugin for WordPress is vulnerable to Privilege Escalation in all versions up to, and including, 5.0.3. The 5.0.3 patch introduced a wphash()/hashequals() signature gate on the pt-paytium-user-data field, but left a second filter — ptcfcheckoutmeta(), registered on the ptmetavalues hook after the signed builder — that copies every $POST['ptformfield'][] key verbatim into the payment meta array without any signature verification; this allows the pt-user-role value it copies to overwrite the signed path's output, after which paytiumuserdataprocessing() reads the persisted pt-user-role post meta and passes it directly as the role argument to wpinsertuser(). This makes it possible for unauthenticated attackers to register a new WordPress account with the administrator role and fully take over the site. Exploitation requires submitting a payment through a publicly-exposed [paytium] shortcode form and completing the resulting payment flow, after which the attacker can seize the new administrator account via the standard lost-password flow on their supplied email address.