Forminator Forms < 1.57.2.1 - Unauthenticated Stored XSS via 'postdata-1[post-custom]' Parameter

Description

The plugin is vulnerable to Stored Cross-Site Scripting via the 'postdata-1[post-custom]' parameter 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.