AChecker 1.5 allows remote attackers to read the contents of arbitrary files via the download.php path parameter by using Unauthenticated Path Traversal. This occurs through readfile in PHP. NOTE: This vulnerability only affects products that are no longer supported by the maintainer.
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.