The Gutenberg Forms plugin for WordPress is vulnerable to arbitrary file uploads due to the users can specify the allowed file types in the 'upload' function in versions up to, and including, 2.2.9. This makes it possible for unauthenticated attackers to upload arbitrary files on the affected site's server which may make remote code execution possible.
https://plugins.trac.wordpress.org/browser/forms-gutenberg/tags/2.2.9/triggers/email.php#L268
https://plugins.trac.wordpress.org/browser/forms-gutenberg/tags/2.2.9/Utils/Bucket.php#L19