QuickShare File Server 1.2.1 contains a path traversal vulnerability in its FTP service due to improper sanitation of user-supplied file paths. Authenticated users can exploit this flaw by submitting crafted sequences to access or write files outside the intended virtual directory. When the "Writable" option is enabled (default during account creation), this allows attackers to upload arbitrary files to privileged locations such as system32, enabling remote code execution via MOF injection or executable placement.
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.