compose.php in @Mail WebMail Client in AtMail Open-Source before 1.05 does not properly handle ../ (dot dot slash) sequences in the unique parameter, which allows remote attackers to conduct directory traversal attacks and read arbitrary files via a ..././ (dot dot dot slash dot slash) sequence.
Improper Limitation of a Pathname to a Restricted Directory 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.