In FusionPBX up to v4.5.7, the file app\xml_cdr\xml_cdr_delete.php uses an unsanitized "rec" variable coming from the URL, which is base64 decoded and allows deletion of any file of the system.
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.