In FusionPBX up to 4.5.7, the file app\contacts\contact_edit.php uses an unsanitized "query_string" variable coming from the URL, which is reflected in HTML, leading to XSS.
https://resp3ctblog.wordpress.com/2019/10/19/fusionpbx-xss-6/
https://github.com/fusionpbx/fusionpbx/commit/cc820b2eb12a3b7070afdcb7f977f70a1d49ce49