The JetFormBuilder — Dynamic Blocks Form Builder plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via 'jfb_xss' (URL Query Variable) Parameter via Calculated Field in all versions up to, and including, 3.6.5.3 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link. Exploitation requires the targeted page to host a form configured with both a URL Query Variable preset field and a Calculated Field that references it, which are standard plugin features.