TYPO3 is an open source PHP based web content management system released under the GNU GPL. It has been discovered that the `FileDumpController` (backend and frontend context) is vulnerable to cross-site scripting when malicious files are displayed using this component. A valid backend user account is needed to exploit this vulnerability. Update to TYPO3 version 7.6.58 ELTS, 8.7.48 ELTS, 9.5.37 ELTS, 10.4.32 or 11.5.16 that fix the problem. There are no known workarounds for this issue.