The Install Tool exposes the current TYPO3 version number to non-authenticated users.
github.com/FriendsOfPHP/security-advisories/blob/master/typo3/cms/2018-12-11-5.yaml
github.com/TYPO3/typo3
github.com/TYPO3/typo3/commit/232d0a64282382229c205904173a16a581555fe3
github.com/TYPO3/typo3/commit/b4dd20f31d483f6399e8bcbffcac3e16a2df0d92
github.com/TYPO3/typo3/commit/fab0cbc970b709ed65fc4622a2cbd52a197480c4
typo3.org/security/advisory/typo3-core-sa-2018-010