TYPO3 Fluid Engine (package typo3fluid/fluid) before versions 2.0.5, 2.1.4, 2.2.1, 2.3.5, 2.4.1, 2.5.5 or 2.6.1 is vulnerable to cross-site scripting when making use of the ternary conditional operator in templates like {showFullName ? fullName : defaultValue}. Updated versions of this package are bundled in following TYPO3 (typo3/cms-core) versions as well: TYPO3 v8.7.25 (using typo3fluid/fluid v2.5.4) and TYPO3 v9.5.6 (using typo3fluid/fluid v2.6.1).