Second-order XSS via skipped custom-element hook
Published Jul 24, 2026 · Updated Jul 24, 2026
Cross-site scripting in Cure53 DOMPurify before 3.4.12 allows attackers to preserve attributes that feed application HTML sinks. In _sanitizeDisallowedNode, a matching CUSTOM_ELEMENT_HANDLING.tagNameCheck returns before _sanitizeElements dispatches afterSanitizeElements, so hook-based attribute removal is skipped. Exploitation requires enabled custom-element handling, a policy hook, and a custom element that later inserts the retained value into an HTML sink.
Summary
What happened
Cross-site scripting in Cure53 DOMPurify before 3.4.12 allows attackers to preserve attributes that feed application HTML sinks. In _sanitizeDisallowedNode, a matching CUSTOM_ELEMENT_HANDLING.tagNameCheck returns before _sanitizeElements dispatches afterSanitizeElements, so hook-based attribute removal is skipped. Exploitation requires enabled custom-element handling, a policy hook, and a custom element that later inserts the retained value into an HTML sink.
The record
- CVE
- CVE-2026-66010
- Published
- Jul 24, 2026
- Updated
- Jul 24, 2026
- Vendor
- Cure53
- Product
- DOMPurify
- Classifications
- CWE-693, CWE-184, CWE-79, T1203
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 24, 2026CVE publishedPublication date reported by the CVE source.
- Jul 24, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <3.4.12
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- CUSTOM_ELEMENT_HANDLING afterSanitizeElements bypass HTML PoCproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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