CVE-2026-66010 DOMPurify before 3.4.12 Hook Bypass via CUSTOM_ELEMENT_HANDLING
Attackers can bypass DOMPurify hooks to preserve malicious attributes on custom elements, enabling second-order XSS in applications using this library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-66010?
CVE-2026-66010 is a medium-severity cross-site scripting vulnerability in cure53 DOMPurify, published on 24 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
DOMPurify before 3.4.12 fails to execute afterSanitizeElements hook for custom elements allowed via CUSTOM_ELEMENT_HANDLING.tagNameCheck, allowing attributes to bypass application security policies. Attackers can preserve sensitive attributes on custom elements that later re-inject them into innerHTML sinks, creating second-order XSS gadgets.
Weakness: CWE-79
Which versions are affected by CVE-2026-66010?
2 open source packages ship an affected version, including dompurify. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
dompurify npm | All versions | 3.4.12 |
dompurify npm | All versions | 3.4.12 |
Products include Cure53 Dompurify.
How do I fix CVE-2026-66010?
Upgrade dompurify to 3.4.12 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-66010 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-66010 exists.
Other vulnerabilities in cure53 DOMPurify
- CVE-2024-47875 DOMPurify nesting-based mXSS
- CVE-2024-48910 DOMPurify vulnerable to tampering by prototype polution
- CVE-2026-47423 DOMPurify XSS via `selectedcontent` re-clone
- CVE-2024-45801 Tampering by prototype polution in DOMPurify
- CVE-2026-49978 DOMPurify IN_PLACE Sanitization Bypass via Attached Shadow Root Inside <template>.content
Sources
Also known as CLEANSTART-2026-DT43318, CLSA-2026-1784769541, CLSA-2026-1784769611, CLSA-2026-1784943203, CLSA-2026-1784943304, CLSA-2026-1791798931 and 28 more.