TYPO3-CORE-SA-2026-006: By-passing Cross-Site Scripting Protection in HTML Sanitizer
It has been discovered that TYPO3 CMS is vulnerable to cross-site scripting.
- Component Type: TYPO3 CMS
- Subcomponent: HTML Sanitizer (based on typo3/html-sanitizer)
- Release Date: June 9, 2026
- Vulnerability Type: Cross-Site Scripting
- Affected Versions: 10.0.0-10.4.56, 11.0.0-11.5.50, 12.0.0-12.4.45, 13.0.0-13.4.30, 14.0.0-14.3.2
- Severity: Medium
- Suggested CVSS: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
- References: CVE-2026-47344, CVE-2026-47345, CWE-79
Problem Description
The typo3/html-sanitizer package allows bypassing the cross-site scripting prevention mechanism:
- CVE-2026-47344: When ALLOW_INSECURE_RAW_TEXT is enabled, whitespace-variant closing tags (e.g., </style\\t>) are not recognized by the sanitizer but accepted by browsers as valid end tags, allowing subsequent content to escape sanitization.
- CVE-2026-47345: Namespace attributes are not encoded correctly during HTML serialization. This allows bypassing the cross-site scripting prevention mechanism of typo3/html-sanitizer.
Solution
Update to TYPO3 versions 10.4.57 ELTS, 11.5.51 ELTS, 12.4.46 ELTS, 13.4.31 LTS, 14.3.3 LTS that fix the problem described.
Credits
Thanks to IPC Labs and Doyensec in collaboration with Claude and Anthropic Research for reporting these issues, and to TYPO3 core & security team members Benjamin Franzke and Oliver Hader for fixing them.
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 you can easily look them up in our review system.
