Sandboxie-Plus is an open source sandbox-based isolation software for Windows. Prior to 1.18.6, a process inside a sandbox could send MSGID_FILE_SET_ATTRIBUTES or MSGID_FILE_SET_SHORT_NAME to SbieSvc and cause the SYSTEM service to open and modify an existing file outside the sandbox. The direct primitive changes file attributes, timestamps, writeability, or 8.3 short names; a short-name redirection can additionally contribute to SYSTEM code execution when a privileged process resolves an attacker-controlled short-name path in a location SbieSvc can open. This vulnerability is fixed in 1.18.6.