GHSA-998c-q8hh-h8gv is a medium-severity (CVSS 4.8) Cross-site Scripting (XSS) vulnerability in concrete5/concrete5. A fix is available for concrete5/concrete5 — see the affected versions and patch details below.
Concrete CMS stored XSS vulnerability in the "Top Navigator Bar" block
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 GHSA-998c-q8hh-h8gv.
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-998c-q8hh-h8gv 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 377,166 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
concrete5/concrete5Real-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
Concrete CMS versions 9.0.0 through 9.3.3 are affected by a stored XSS vulnerability in the "Top Navigator Bar" block. Since the "Top Navigator Bar" output was not sufficiently sanitized, a rogue administrator could add a malicious payload that could be executed when targeted users visited the home page. This does not affect versions below 9.0.0 since they do not have the Top Navigator Bar Block. Thanks, Chu Quoc Khanh for reporting.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | concrete5/concrete5 | ≥ 9.0.0&&< 9.3.3 | 9.3.3composer require concrete5/concrete5:^9.3.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for concrete5/concrete5, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update concrete5/concrete5 to 9.3.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-998c-q8hh-h8gv 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-998c-q8hh-h8gv can be triaged on real exposure rather than presence alone.
Tailored to GHSA-998c-q8hh-h8gv. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-998c-q8hh-h8gv in your dependencies?
O3 Security finds GHSA-998c-q8hh-h8gv across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.