TYPO3 before 4.1.14, 4.2.x before 4.2.13, 4.3.x before 4.3.4 and 4.4.x before 4.4.1 contains an insecure default value of the variable fileDenyPattern which could allow remote attackers to execute arbitrary code on the backend.
The page module in TYPO3 before 8.7.11, and 9.1.0, has XSS via $GLOBALS['TYPO3_CONF_VARS']['SYS']['sitename'], as demonstrated by an admin entering a crafted site name during the installation process.
Extbase in TYPO3 4.3.0 before 6.2.24, 7.x before 7.6.8, and 8.1.1 allows remote attackers to obtain sensitive information or possibly execute arbitrary code via a crafted Extbase action.
The sanitizeLocalUrl function in TYPO3 6.x before 6.2.15, 7.x before 7.4.0, 4.5.40, and earlier allows remote authenticated users to bypass the XSS filter and conduct cross-site scripting (XSS) attacks via a base64 encoded data URI, as demonstrated by the (1) returnUrl parameter to show_rechis.php and the (2) redirect_url parameter to index.php.