TYPO3 is an open source PHP based web content management system released under the GNU GPL. The plaintext value of `$GLOBALS['SYS']['encryptionKey']` was displayed in the editing forms of the TYPO3 Install Tool user interface. This allowed attackers to utilize the value to generate cryptographic hashes used for verifying the authenticity of HTTP request parameters. Exploiting this vulnerability requires an administrator-level backend user account with system maintainer permissions. Users are advised to update to TYPO3 versions 8.7.57 ELTS, 9.5.46 ELTS, 10.4.43 ELTS, 11.5.35 LTS, 12.4.11 LTS, 13.0.1 that fix the problem described. There are no known workarounds for this vulnerability.