Failing to properly dissociate system related configuration from user generated configuration, the Form Framework (system extension βformβ) is vulnerable to SQL injection and Privilege Escalation. Basically instructions can be persisted to a form definition file that were not configured to be modified - this applies to definitions managed using the form editor module as well as direct file upload using the regular file list module. A valid backend user account as well as having system extension form activated are needed in order to exploit this vulnerability.
github.com/FriendsOfPHP/security-advisories/blob/master/typo3/cms-core/2018-07-12-3.yaml
github.com/TYPO3-CMS/core
github.com/TYPO3-CMS/core/commit/5e3ed52854ea8192f1c0e2ef30f434e74ba6d253
github.com/TYPO3-CMS/core/commit/a0a6271dc8f715b5b6859771333d57925dfb63bc
github.com/TYPO3-CMS/core/commit/e70d7c66110a0919b39bccdfdc73cbfd7f504dfc
github.com/TYPO3-CMS/core/commit/eddc7635fb3447f0fb69831855f4095de8e12350
typo3.org/security/advisory/typo3-core-sa-2018-003