The Fluent Forms – Customizable Contact Forms, Survey, Quiz, & Conversational Form Builder plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the 'any attacker-chosen name matching the {get.NAME} placeholder (PoC uses 'proof')' parameter in all versions up to, and including, 6.2.14 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 a site administrator to have configured a Custom HTML field on a published form containing a {get.*} SmartCode inside a URL-accepting attribute such as iframe src or a href — a documented Fluent Forms feature.
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