PoC

# CVE-2026-30830: defuddle XSS — Fixed in 0.9.0 📦 npm Not in CISA KEV # CVE-2026-30830 — defuddle [Fix: kepano/defuddle@f154cb7](https://github.com/kepano/defuddle/commit/f154cb740ee603431b69638273af737a27156df9) CVE-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 Also known as[GHSA-5mq8-78gm-pjmq](/vulnerability/GHSA-5mq8-78gm-pjmq) Published Mar 7, 2026 Updated Oct 28, 2026 Affected 1 pkg Patched 1 / 1 Exploits None indexed Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS) ## 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 [via FIRST.org ↗](https://www.first.org/epss/) 0.3%probability of exploitation in next 30 days Lower Risk+0.02% Lower risk than most CVEs22th percentile — riskier than 22% of all scored CVEsHighest risk 0.00%0.26%0.53%0.79%0.0%0.3%May 26Sep 26Nov 26 Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/). ## Real-World Exposure 1 pkg affected 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. 172other npm packages depend on this — each one inherits the vulnerability until it's patched upstream `defuddle`npm 1.5Mdownloads / week ## Description #### Summary The `_findContentBySchemaText` method in `src/defuddle.ts` interpolates image `src` and `alt` attributes directly into an HTML string without escaping: ``` html += ` ${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: ``` PoC

Short.

Extra text to inflate parent word count padding padding padding.

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.

``` Output: ``` pwned

``` 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 1 total 1 fixed Ecosystem Package Vulnerable range Fix 📦npm `defuddle` all versions 0.9.0`npm install defuddle@0.9.0` ## Affected Products 1 product · 1 configurations Application `defuddle`kepano < 0.9.0 range ## Detection & mitigation playbook Open-source dependency 1. ### Detect 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. 2. ### 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. 3. ### 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 \### Summary The \`\_findContentBySchemaText\` method in \`src/defuddle.ts\` interpolates image \`src\` and \`alt\` attributes directly into an HTML string without escaping: \`\`\`typescript html += \` ${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 sibl O3 Security · Impact-Aware SCA ### Is CVE-2026-30830 in your dependencies? Find it across npm, including transitive dependencies. [Scan my dependencies](/book-demo) [How O3 SCA works](/impact-aware-sca)