Problem Description

User submitted content was used without being properly encoded in HTML emails sent to users. The actually affected components were mail clients used to view those messages.

Solution

Update to TYPO3 versions 9.5.35 ELTS, 10.4.29, 11.5.11 that fix the problem described above.

Credits

Thanks to Christian Seifert who reported this issue and to TYPO3 framework merger Andreas Fernandez who fixed the issue.

General Advice

Follow the recommendations that are given in the TYPO3 Security Guide. Please subscribe to the typo3-announce mailing list.

General Note

All security related code changes are tagged so that you can easily look them up in our review system.