In FusionPBX up to 4.5.7, the file app\contacts\contact_addresses.php uses an unsanitized "id" variable coming from the URL, which is reflected in HTML, leading to XSS.
https://resp3ctblog.wordpress.com/2019/10/19/fusionpbx-xss-5/
https://github.com/fusionpbx/fusionpbx/commit/913ad234cf145a55e5f2faaab08d776d83c1699b