WiX toolset lets developers create installers for Windows Installer, the Windows installation engine. The custom action behind WiX's `RemoveFolderEx` functionality could allow a standard user to delete protected directories. `RemoveFolderEx` deletes an entire directory tree during installation or uninstallation. It does so by recursing every subdirectory starting at a specified directory and adding each subdirectory to the list of directories Windows Installer should delete. If the setup author instructed `RemoveFolderEx` to delete a per-user folder from a per-machine installer, an attacker could create a directory junction in that per-user folder pointing to a per-machine, protected directory. Windows Installer, when executing the per-machine installer after approval by an administrator, would delete the target of the directory junction. This vulnerability is fixed in 3.14.1 and 4.0.5.
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.