CVE-2020-26227
MEDIUMCVE-2020-26227 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in typo3/cms-core. 2 public exploit references exist, so weaponization risk is real. O3 Security confirms whether CVE-2020-26227 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Cross-Site Scripting in Fluid view helpers
Real-World Exposure
typo3/cms-core🐘typo3/cms-core🐘typo3/cms-core🐘typo3/cms🐘typo3/cms🐘typo3/cmsReal-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
TYPO3 is an open source PHP based web content management system. In TYPO3 before versions 9.5.23 and 10.4.10 the system extension Fluid (typo3/cms-fluid) of the TYPO3 core is vulnerable to cross-site scripting passing user-controlled data as argument to Fluid view helpers. Update to TYPO3 versions 9.5.23 or 10.4.10 that fix the problem described.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | typo3/cms-core | ≥ 9.0.0&&< 9.5.23 | 9.5.23 |
| 🐘Packagist | typo3/cms-core | ≥ 10.0.0&&< 10.4.10 | 10.4.10 |
| 🐘Packagist | typo3/cms-core | ≥ 8.7.0&&< 8.7.38 | 8.7.38 |
| 🐘Packagist | typo3/cms | ≥ 10.0.0&&< 10.4.10 | 10.4.10 |
| 🐘Packagist | typo3/cms | ≥ 9.0.0&&< 9.5.23 | 9.5.23 |
| 🐘Packagist | typo3/cms | ≥ 8.7.0&&< 8.7.38 | 8.7.38 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for typo3/cms-core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update typo3/cms-core to 9.5.23 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-26227 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2020-26227 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2020-26227. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2020-26227 in your dependencies?
O3 detects CVE-2020-26227 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.