CVE-2023-38500 is a medium-severity (CVSS 4.7) Cross-site Scripting (XSS) vulnerability in typo3/html-sanitizer. A fix is available for typo3/html-sanitizer — see the affected versions and patch details below.
By-passing Cross-Site Scripting Protection in HTML Sanitizer
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-38500.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
typo3/html-sanitizer🐘typo3/html-sanitizerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
CVSS:
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N/E:F/RL:O/RC:C(4.4)
Problem
Due to an encoding issue in the serialization layer, malicious markup nested in a noscript element was not encoded correctly. noscript is disabled in the default configuration, but might have been enabled in custom scenarios. This allows bypassing the cross-site scripting mechanism of typo3/html-sanitizer.
Solution
Update to typo3/html-sanitizer versions 1.5.1 or 2.1.2 that fix the problem described.
Credits
Thanks to David Klein and Yaniv Nizry who reported this issue, and to TYPO3 security team members Oliver Hader and Benjamin Franzke who fixed the issue.
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | typo3/html-sanitizer | ≥ 1.0.0&&< 1.5.1 | 1.5.1composer require typo3/html-sanitizer:^1.5.1 |
| 🐘Packagist | typo3/html-sanitizer | ≥ 2.0.0&&< 2.1.2 | 2.1.2composer require typo3/html-sanitizer:^2.1.2 |
Affected Products
html sanitizertypo3Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for typo3/html-sanitizer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update typo3/html-sanitizer to 1.5.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-38500 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is CVE-2023-38500 in your dependencies?
Find it across Packagist, including transitive dependencies.