Contao is an Open Source CMS. In affected versions authenticated users in the back end can list files outside the document root in the file selector widget. Users are advised to update to Contao 4.13.49. There are no known workarounds for this vulnerability.
https://github.com/contao/contao/security/advisories/GHSA-4p75-5p53-65m9
https://contao.org/en/security-advisories/directory-traversal-in-the-fileselector-widget