The Mollie Forms plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 2.6.13. This is due to missing or incorrect nonce validation on the duplicateForm() function. This makes it possible for unauthenticated attackers to duplicate forms via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.
https://plugins.trac.wordpress.org/changeset/3097426/mollie-forms