TYPO3 Improper Input Validation Vulnerability - CVE-2020-15099

In TYPO3 CMS greater than or equal to 9.0.0 and less than 9.5.20 and greater than or equal to 10.0.0 and less than 10.4.6 in a case where an attacker manages to generate a valid cryptographic message authentication code (HMAC-SHA1) - either by using a different existing vulnerability or in case the internal encryptionKey was exposed - it is possible to retrieve arbitrary files of a TYPO3 installation. This includes the possibility to fetch typo3conf/LocalConfiguration.php which again contains the encryptionKey as well as credentials of the database management system being used. In case a database server is directly accessible either via internet or in a shared hosting network this allows the ability to completely retrieve manipulate or delete database contents. This includes creating an administration user account - which can be used to trigger remote code execution by injecting custom extensions. This has been patched in versions 9.5.20 and 10.4.6.