An issue was discovered in the direct_mail (aka Direct Mail) extension through 9.5.1 for TYPO3. The Configuration backend module of the extension allows an authenticated user to write to an arbitrary TSConfig page for folders configured as Direct Mail. Exploiting this may lead to Configuration Injection (TYPO3 10.4 and above) and to Arbitrary Code Execution (TYPO3 9.5 and below). A valid backend user account, with access to the Direct Mail Configuration backend module, is needed to exploit this.