TYPO3 is an open source PHP based web content management system. In TYPO3 before versions 9.5.23 and 10.4.10 the system extension Fluid (typo3/cms-fluid) of the TYPO3 core is vulnerable to cross-site scripting passing user-controlled data as argument to Fluid view helpers. Update to TYPO3 versions 9.5.23 or 10.4.10 that fix the problem described.
https://typo3.org/security/advisory/typo3-core-sa-2020-010
https://github.com/TYPO3/TYPO3.CMS/security/advisories/GHSA-vqqx-jw6p-q3rf