CVE-2023-36806 is a medium-severity (CVSS 6.5) Cross-site Scripting (XSS) vulnerability in contao/core-bundle. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for contao/core-bundle — see the affected versions and patch details below.
Contao cross site scripting vulnerability via input unit widget
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-36806.
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
contao/core-bundle🐘contao/core-bundle🐘contao/core-bundleReal-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
Contao is an open source content management system. Starting in version 4.0.0 and prior to versions 4.9.42, 4.13.28, and 5.1.10, it is possible for untrusted backend users to inject malicious code into headline fields in the back end, which will be executed both in the element preview (back end) and on the website (front end). Installations are only affected if there are untrusted back end users who have the rights to modify headline fields, or other fields using the input unit widget. Contao 4.9.42, 4.13.28, and 5.1.10 have a patch for this issue. As a workaround, disable the login for all untrusted back end users.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | contao/core-bundle | ≥ 4.0.0&&< 4.9.42 | 4.9.42composer require contao/core-bundle:^4.9.42 |
| 🐘Packagist | contao/core-bundle | ≥ 4.10.0&&< 4.13.28 | 4.13.28composer require contao/core-bundle:^4.13.28 |
| 🐘Packagist | contao/core-bundle | ≥ 5.0.0&&< 5.1.10 | 5.1.10composer require contao/core-bundle:^5.1.10 |
Affected Products
contaocontaoResearch 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 contao/core-bundle, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update contao/core-bundle to 4.9.42 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-36806 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-2023-36806 in your dependencies?
Find it across Packagist, including transitive dependencies.