The Form Maker plugin for WordPress is vulnerable to Stored Cross-Site Scripting via hidden field values in all versions up to, and including, 1.15.35. This is due to insufficient output escaping when displaying hidden field values in the admin submissions list. The plugin uses html_entity_decode() on user-supplied hidden field values without subsequent escaping before output, which converts HTML entity-encoded payloads back into executable JavaScript. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in the admin submissions view that will execute whenever an administrator accesses the submissions list.