GHSA-4wx8-5gm2-2j97 is a high-severity (CVSS 7.6) Cross-site Scripting (XSS) vulnerability in github.com/filebrowser/filebrowser/v2. A fix is available for github.com/filebrowser/filebrowser/v2 — see the affected versions and patch details below.
filebrowser allows Stored Cross-Site Scripting through the Markdown preview function
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 GHSA-4wx8-5gm2-2j97.
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-4wx8-5gm2-2j97 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
github.com/filebrowser/filebrowser/v2🐹github.com/filebrowser/filebrowserReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Summary
The Markdown preview function of File Browser v2.32.0 is vulnerable to Stored Cross-Site-Scripting (XSS). Any JavaScript code that is part of a Markdown file uploaded by a user will be executed by the browser
Impact
A user can upload a malicious Markdown file to the application which can contain arbitrary HTML code. If another user within the same scope clicks on that file, a rendered preview is opened. JavaScript code that has been included will be executed.
Malicious actions that are possible include:
- Obtaining a user's session token
- Elevating the attacker's privileges, if the victim is an administrator (e.g., gaining command execution rights)
Vulnerability Description
Most Markdown parsers accept arbitrary HTML in a document and try rendering it accordingly. For instance, if one creates a file called xss.md with the following content:
# Hallo
<b>foo</b>
<img src="xx" onerror=alert(9)>
<i>bar</i>
Bold and italic text will be rendered. Also, the renderer used in File Browser will try to display the image and execute the code in the onerror event handler.
Proof of Concept
The screenshot shows that the code from the file mentioned above has actually been executed in the victim's browser:
Recommended Countermeasures
The most thorough fix would be to reconfigure the application's Markdown parser to ignore all HTML elements and only render rich text which is part of the Markdown specification. If HTML rendering is considered to be a required feature, an HTML sanitizer like DOMPurify should be used, preferably in conjunction with a Content Security Policy (CSP).
Timeline
2025-03-25Identified the vulnerability in version 2.32.02025-04-11Contacted the project2025-04-18Vulnerability disclosed to the project2025-06-25Uploaded advisories to the project's GitHub repository2025-06-26CVE ID assigned by GitHub2025-06-26Fix released with version 2.33.7
References
Credits
- Mathias Tausig (SBA Research)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/filebrowser/filebrowser/v2 | all versions | 2.33.7go get github.com/filebrowser/filebrowser/v2@v2.33.7 |
| 🐹Go | github.com/filebrowser/filebrowser | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/filebrowser/filebrowser/v2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/filebrowser/filebrowser/v2 to 2.33.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4wx8-5gm2-2j97 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-4wx8-5gm2-2j97 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-4wx8-5gm2-2j97. 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-4wx8-5gm2-2j97 in your dependencies?
O3 Security finds GHSA-4wx8-5gm2-2j97 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.