The Fluent Forms plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the form-submission.js script in all versions up to, and including, 6.0.2 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with Contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
https://wordpress.org/plugins/fluentform/#developers
https://plugins.trac.wordpress.org/changeset/3274693/
https://plugins.trac.wordpress.org/browser/fluentform/tags/6.0.2/assets/js/form-submission.js