SimpleForm <= 3.10.0 - Unauthenticated Privilege Escalation to wp_capabilities Mass Assignment via simpleform_wp_register

The SimpleForm – Form Maker to Chat Apps with Quiz, Poll and Multi Lead Notifications plugin for WordPress is vulnerable to Privilege Escalation in all versions up to, and including, 3.10.0 This is due to the wp_ajax_nopriv_simpleform_wp_register AJAX action lacking any capability check for role assignment and the save_custom_fields_to_user_meta() function using an exclusion list that omits wp_capabilities, combined with get_form_settings() returning a hard-coded defaults array that unconditionally enables meta writing regardless of the supplied form_id. This makes it possible for unauthenticated attackers to create a new Administrator-level WordPress account by supplying wp_capabilities[administrator]=1 alongside standard registration fields. The nonce required by the endpoint is publicly emitted into the front_end_data JavaScript object on every front-end page via wp_enqueue_scripts, making it trivially obtainable by any unauthenticated visitor before submitting the malicious request.