TYPO3 allows remote authenticated backend users to unserialize arbitrary objects

viewhelp.php in the backend help system in TYPO3 4.5.x before 4.5.19, 4.6.x before 4.6.12 and 4.7.x before 4.7.4 allows remote authenticated backend users to unserialize arbitrary objects and possibly execute arbitrary PHP code via an unspecified parameter, related to a "missing signature HMAC."...