Component Type: Third party extension. This extension is not part of the TYPO3 default installation.
Affected Versions: Version 4.0.3 and below
Vulnerability Type: Cross Site Scripting, Remote Code Execution
Solution: An updated version is available from the TYPO3 extension manager and at typo3.org/extensions/repository/view/th_mailformplus/4.0.4/.
At the time of writing, the most recent version of MailformPlus is version 4.0.7 which is available at typo3.org/extensions/repository/view/th_mailformplus/4.0.7/.
Credits: Credits go to security team member Marcus Krause, who discovered the issue. Furthermore the TYPO3 Security Team wishes to thank the guys at Typoheads GmbH. After being informed by the TYPO3 Security Team about the presence of security issues, they have fixed the issues quickly.