In FusionPBX up to v4.5.7, the file app/music_on_hold/music_on_hold.php uses an unsanitized "file" variable coming from the URL, which takes any pathname (base64 encoded) and allows a download of it.
https://resp3ctblog.wordpress.com/2019/10/19/fusionpbx-path-traversal-3/
https://github.com/fusionpbx/fusionpbx/commit/95ed18aa9d781f232f5686a9027bb6f677c9b8da