JetFormBuilder 3.5.6.2 - 3.6.5.2 - Admin+ Arbitrary File Deletion via Server-Side Validation Callback

The JetFormBuilder — Dynamic Blocks Form Builder WordPress plugin before 3.6.5.3 does not sufficiently restrict which PHP functions can be used as a custom field-validation callback, relying on a blocklist that omits a file-deletion function, allowing users able to manage forms to cause arbitrary files on the server to be deleted. The deletion itself is carried out when the form is submitted, which requires no authentication.