GHSA-5mq8-78gm-pjmq is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in defuddle. O3 Security confirms whether GHSA-5mq8-78gm-pjmq is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
defuddle vulnerable to XSS via unescaped string interpolation in _findContentBySchemaText image tag
Real-World Exposure
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Description
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 | 0.9.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for defuddle. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update defuddle to 0.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5mq8-78gm-pjmq 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 pinpoints whether GHSA-5mq8-78gm-pjmq is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-5mq8-78gm-pjmq. 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-5mq8-78gm-pjmq in your dependencies?
O3 detects GHSA-5mq8-78gm-pjmq across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.