GHSA-m8x6-6r63-qvj2 is a high-severity (CVSS 7.2) Cross-site Scripting (XSS) vulnerability in contao/core-bundle. A fix is available for contao/core-bundle — see the affected versions and patch details below.
Cross site scripting via canonical tag in Contao
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- 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 GHSA-m8x6-6r63-qvj2.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-m8x6-6r63-qvj2 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
contao/core-bundle🐘contao/contaoReal-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
Impact
Untrusted users can inject malicious code into the canonical tag, which is then executed on the web page (front end).
Patches
Update to Contao 4.13.3.
Workarounds
Disable canonical tags in the root page settings.
References
https://contao.org/en/security-advisories/cross-site-scripting-via-canonical-url
For more information
If you have any questions or comments about this advisory, open an issue in contao/contao.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | contao/core-bundle | ≥ 4.13.0&&< 4.13.3 | 4.13.3composer require contao/core-bundle:^4.13.3 |
| 🐘Packagist | contao/contao | ≥ 4.13.0&&< 4.13.3 | 4.13.3composer require contao/contao:^4.13.3 |
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 4.13.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-m8x6-6r63-qvj2 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-m8x6-6r63-qvj2 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-m8x6-6r63-qvj2. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
How to detect GHSA-m8x6-6r63-qvj2
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id ghsa-m8x6-6r63-qvj2 -u https://target- Template
- Contao <4.13.3 - Cross-Site Scripting
- Severity
- medium
- Impact
- Successful exploitation of this vulnerability could allow an attacker to execute malicious scripts in a victim's browser, leading to potential data theft, session hijacking, or defacement of the affected website.
- Remediation
- As a workaround, users may disable canonical tags in the root page settings.
Template by ProjectDiscovery nuclei-templates (ritikchaddha), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is GHSA-m8x6-6r63-qvj2 in your dependencies?
O3 Security finds GHSA-m8x6-6r63-qvj2 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.