GHSA-87xg-pxx2-7hvx
HIGHGHSA-87xg-pxx2-7hvx is a high-severity (CVSS 8.2) Cross-site Scripting (XSS) vulnerability in dompurify. O3 Security confirms whether GHSA-87xg-pxx2-7hvx is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
DOMPurify XSS via selectedcontent re-clone
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-87xg-pxx2-7hvx.
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-87xg-pxx2-7hvx 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 366,357 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
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.
dompurifynpmDescription
Summary
DOMPurify 3.4.4 allows selectedcontent by default, allowing a chain in which browsers "re-clone" an XSS payload after sanitization, effectively bypassing DOMPurify.
Details
The chain is as follows:
- The browser parses the input and creates a
<selectedcontent>clone from the selected<option> - DOMPurify walks and sanitizes that generated clone.
- DOMPurify reaches the original
<option>and removesselected=javascript:1 - The browser refreshes the
<selectedcontent>clone from the originaloption's content. - The refreshed clone is in a subtree DOMPurify already walked, which DOMPurify doesn't go back to sanitize
- The returned string contains unsanitized markup inside
<selectedcontent>.
PoC
const dirty =
'<select><button><selectedcontent></selectedcontent></button>' +
'<option selected=javascript:1>' +
'<img src=x onerror=alert(1)>x' +
'</option></select>';
const clean = DOMPurify.sanitize(dirty);
console.log(clean);
document.body.innerHTML = clean;
Observed "sanitized" output in Chromium 148/WebKit 625:
<select><button><selectedcontent><img src="x" onerror="alert(1)">x</selectedcontent></button><option><img src="x">x</option></select>
After reinsertion, the browser updates the live DOM and strips the handler from the displayed clone, but the onerror has already fired:
<select><button><selectedcontent><img src="x">x</selectedcontent></button><option><img src="x">x</option></select>
Reproduced in Chromium and WebKit, but not Safari (not yet latest WebKit) or Firefox. Will likely change with browser support for selectedcontent.
Impact
This is a default-configuration DOMPurify sanitizer bypass resulting in XSS.
Applications are impacted if they sanitize attacker-controlled HTML with DOMPurify 3.4.4 using the string-input path and then insert the returned string into the page, for example with innerHTML.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | dompurify | ≥ 3.4.4&&< 3.4.5 | 3.4.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for dompurify. 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 dompurify to 3.4.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-87xg-pxx2-7hvx 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-87xg-pxx2-7hvx 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-87xg-pxx2-7hvx. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This is a cross-site scripting (XSS) vulnerability in DOMPurify, a sanitizer for HTML, MathML, and SVG. The flaw allows a remote attacker to bypass sanitization by crafting a malicious payload that leverages the default allowance of `selectedcontent`. This can lead to browsers re-cloning the payload and executing…
Frequently Asked Questions
Is GHSA-87xg-pxx2-7hvx in your dependencies?
O3 detects GHSA-87xg-pxx2-7hvx across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.