In FusionPBX up to v4.5.7, the file app\edit\filedelete.php uses an unsanitized "file" variable coming from the URL, which is reflected in HTML, leading to XSS.
https://resp3ctblog.wordpress.com/2019/10/19/fusionpbx-xss-20/
https://github.com/fusionpbx/fusionpbx/commit/cd4632b46c62855f7e1c1c93d20ffd64edcb476e