DOMPurify before 3.4.12 Hook Bypass via CUSTOM_ELEMENT_HANDLING (CVE-2026-66010) | HOL Guard CVE

Medium · CVSS 6.1CVE-2026-66010

DOMPurify before 3.4.12 Hook Bypass via CUSTOM_ELEMENT_HANDLING

Answer in brief

CVE-2026-66010 records a Medium severity (CVSS 6.1) vulnerability in DOMPurify before 3.4.12 Hook Bypass via CUSTOM_ELEMENT_HANDLING. The current sources do not mark it as known exploited. The current feed maps cure53/DOMPurify (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jul 24, 2026Updated Sep 17, 2026Source checked Sep 17, 2026First seen by HOL Aug 6, 2026Material review Sep 17, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.1
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 6.1. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps cure53/DOMPurify (generic). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:a:cure53:dompurify::::::::	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
cure53/DOMPurifygeneric	>=0 <3.4.12	3.4.12

Recommended response

Check inventory. Check lockfiles and deployed manifests for cure53/DOMPurify.
Review the reported fix. Update cure53/DOMPurify to 3.4.12 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jul 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 17, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 6, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.