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.
In FusionPBX up to v4.5.7, the file resources\download.php uses an unsanitized "f" variable coming from the URL, which takes any pathname and allows a download of it. (resources\secure_download.php is also affected.)