Contao is an open source content management system. Prior to versions 4.9.40, 4.13.21, and 5.1.4, logged in users can list arbitrary system files in the file manager by manipulating the Ajax request. However, it is not possible to read the contents of these files. Users should update to Contao 4.9.40, 4.13.21 or 5.1.4 to receive a patch. There are no known workarounds.
https://github.com/contao/contao/security/advisories/GHSA-fp7q-xhhw-6rj3
https://github.com/contao/contao/commit/6f3e705f4ff23f4419563d09d8485793569f31df
https://contao.org/en/security-advisories/directory-traversal-in-the-file-manager