Medium [CVE-2026-66010] Cross-Site Scripting (XSS) via custom element attribute bypass
This medium-severity Red Hat Linux advisory covers CVE-2026-66010 affecting Cryostat 4, Migration Toolkit for Virtualization, Multicluster Engine for Kubernetes.
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Summary
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.
A flaw was found in DOMPurify. These attributes can then be re-injected into web page content, leading to Cross-Site Scripting (XSS) attacks.
An attacker could exploit this to execute malicious scripts in a user's browser, potentially leading to information disclosure or unauthorized actions. This Moderate-impact flaw in DOMPurify allows for Cross-Site Scripting (XSS) attacks by enabling the bypass of sanitization policies for custom elements.
An attacker could exploit this by crafting malicious content that, when processed by affected Red Hat products utilizing DOMPurify in their web interfaces, could lead to the execution of arbitrary client-side scripts. Red Hat severity: Moderate — CVSS 6.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N).
Weakness: CWE-79.
Affected products named by the advisory: Cryostat 4; Migration Toolkit for Virtualization; Multicluster Engine for Kubernetes; Node HealthCheck Operator; and 30 more.
- < 3.4.12
Official advisory · high-confidence parse· fetched 5 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 5 days ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Official advisory · high-confidence parse· fetched 5 days ago·verify at source
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