Forminator Forms <= 1.57.2 - Unauthenticated Stored Cross-Site Scripting via 'postdata-1[post-custom]' Parameter

The Forminator Forms – Contact Form, Payment Form & Custom Form Builder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via 'postdata-1[post-custom]' Parameter in all versions up to, and including, 1.57.2 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The required form submission nonce is freely obtainable by unauthenticated users via the publicly accessible wp_ajax_nopriv_forminator_get_nonce endpoint, making the full attack chain exploitable without any authentication or prior account.