Paytium Mollie Payment Forms Plugin Privilege Escalation Vulnerability

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 added a wp_hash()/hash_equals() signature gate on the pt-paytium-user-data field, but a second filter, pt_cf_checkout_meta(), remains registered on the pt_meta_values hook after the signed builder. It copies every $_POST['pt_form_field'][*] key verbatim into the payment meta array without signature verification, allowing the pt-user-role value to overwrite the signed path's output. Later, paytium_user_data_processing() reads the persisted _pt-user-role post meta and passes it directly as the role argument to wp_insert_user().

This lets unauthenticated attackers 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
• Completing the resulting payment flow
• Seizing the new administrator account via the standard lost-password flow on the supplied email address