The Contact Form Plugin by Fluent Forms for Quiz, Survey, and Drag & Drop WP Form Builder plugin for WordPress is vulnerable to unauthorized Malichimp API key update due to an insufficient capability check on the verifyRequest function in all versions up to, and including, 5.1.18. This makes it possible for Form Managers with a Subscriber-level access and above to modify the Mailchimp API key used for integration. At the same time, missing Mailchimp API key validation allows the redirect of the integration requests to the attacker-controlled server.