The wp_ajax_save_fbe_settings and wp_ajax_delete_fbe_settings AJAX actions of the Facebook for WordPress plugin before 3.0.4 were vulnerable to CSRF due to a lack of nonce protection. The settings in the saveFbeSettings function had no sanitization allowing for script tags to be saved.
https://www.wordfence.com/blog/2021/03/two-vulnerabilities-patched-in-facebook-for-wordpress-plugin/
https://wpscan.com/vulnerability/169d21fc-d191-46ff-82e8-9ac887aed8a4