Fluent Forms <= 6.2.1 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'permission_message' Shortcode Attribute

The Fluent Forms – Customizable Contact Forms, Survey, Quiz, & Conversational Form Builder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'permission_message' parameter in all versions up to, and including, 6.2.1 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.