GHSA-x369-mcw8-8rvj — darkreader
LOWGHSA-x369-mcw8-8rvj is a low-severity (CVSS 3.4) Information Exposure vulnerability in darkreader. A fix is available for darkreader — see the affected versions and patch details below.
Dark Reader gives users the ability to request style sheets from local web servers
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-x369-mcw8-8rvj.
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-x369-mcw8-8rvj 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 377,333 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
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
darkreadernpmDescription
Description
Dark Reader versions prior to 4.9.117 included a behavior where a website could request a style sheet from a locally running web server, for example http://localhost:8080/style.css, If an address was available and returned a text/css content type.
Patches
The problem was fixed in version 4.9.117, released on December 3, 2025. Most users received the update automatically. Users running manual builds must upgrade to version 4.9.117 or later.
The installed extension version number can be verified in Dark Reader's menu (More > All settings > About), browser settings, chrome://extensions or about:addons pages.
Users are encouraged not to disable automatic extension updates and use the latest browser version, as browser releases typically include multiple security fixes of varying severity.
NPM package
The issue does not affect developers using the darkreader NPM package for website integration. Developers using the setFetchMethod() API must ensure the cross-origin requests are restricted to the intended scope.
Custom forks
Developers using custom forks of earlier versions of Dark Reader to build other extensions, or integrating it into their apps or browsers, should review their implementation to ensure cross-origin requests are handled securely.
Acknowledgements
Security research performed by Brian Carpenter - Deep Fork Cyber.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | darkreader | all versions | 4.9.117npm install darkreader@4.9.117 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for darkreader, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update darkreader to 4.9.117 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-x369-mcw8-8rvj 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-x369-mcw8-8rvj can be triaged on real exposure rather than presence alone.
Tailored to GHSA-x369-mcw8-8rvj. 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-x369-mcw8-8rvj in your dependencies?
O3 Security finds GHSA-x369-mcw8-8rvj across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.