CVE-2026-65911: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in cure53 DOMPurify
In DOMPurify through 3.3.3, function predicates supplied via ADD_ATTR or ADD_TAGS to DOMPurify.sanitize() persist in internal state (EXTRA_ELEMENT_HANDLING) across subsequent sanitize() calls on the same instance. If a later call on the same instance provides ADD_ATTR or ADD_TAGS as an array rather than a function, the previously set function handler is neither cleared nor overwritten, so it continues to approve attacker-controlled attributes or tags. This can allow dangerous event-handler attributes or forbidden tags (bypassing FORBID_TAGS) to survive sanitization, resulting in cross-site scripting. The vendor (Cure53) considers this an edge case outside DOMPurify's threat model; the referenced advisory lists 3.4.0 as the patched version.
AI Analysis
Technical Summary
CVE-2026-65911 describes a cross-site scripting (XSS) vulnerability in DOMPurify through version 3.3.3. The vulnerability arises because function predicates provided via ADD_ATTR or ADD_TAGS to DOMPurify.sanitize() persist in internal state across multiple sanitize() calls on the same instance. If a subsequent call replaces these with arrays rather than functions, the original function handlers remain active and continue to approve potentially dangerous attributes or tags, including event-handler attributes or forbidden tags that should be blocked. This can lead to XSS by allowing malicious content to survive sanitization. The vendor Cure53 considers this an edge case outside the typical threat model. The vulnerability is fixed in DOMPurify version 3.4.0.
Potential Impact
The vulnerability allows attacker-controlled attributes or tags that are normally forbidden to bypass DOMPurify's sanitization process, potentially enabling cross-site scripting attacks. This can lead to execution of malicious scripts in the context of the affected web application. However, the vendor regards this as an edge case and the CVSS score rates it as medium severity.
Mitigation Recommendations
Upgrade DOMPurify to version 3.4.0 or later, where this issue is fixed. No other official remediation or temporary fixes are documented. Patch status is confirmed by the vendor advisory indicating 3.4.0 as the fixed version.
CVE-2026-65911: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in cure53 DOMPurify
Description
In DOMPurify through 3.3.3, function predicates supplied via ADD_ATTR or ADD_TAGS to DOMPurify.sanitize() persist in internal state (EXTRA_ELEMENT_HANDLING) across subsequent sanitize() calls on the same instance. If a later call on the same instance provides ADD_ATTR or ADD_TAGS as an array rather than a function, the previously set function handler is neither cleared nor overwritten, so it continues to approve attacker-controlled attributes or tags. This can allow dangerous event-handler attributes or forbidden tags (bypassing FORBID_TAGS) to survive sanitization, resulting in cross-site scripting. The vendor (Cure53) considers this an edge case outside DOMPurify's threat model; the referenced advisory lists 3.4.0 as the patched version.
CVSS v4.0
Score 5.1medium
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-65911 describes a cross-site scripting (XSS) vulnerability in DOMPurify through version 3.3.3. The vulnerability arises because function predicates provided via ADD_ATTR or ADD_TAGS to DOMPurify.sanitize() persist in internal state across multiple sanitize() calls on the same instance. If a subsequent call replaces these with arrays rather than functions, the original function handlers remain active and continue to approve potentially dangerous attributes or tags, including event-handler attributes or forbidden tags that should be blocked. This can lead to XSS by allowing malicious content to survive sanitization. The vendor Cure53 considers this an edge case outside the typical threat model. The vulnerability is fixed in DOMPurify version 3.4.0.
Potential Impact
The vulnerability allows attacker-controlled attributes or tags that are normally forbidden to bypass DOMPurify's sanitization process, potentially enabling cross-site scripting attacks. This can lead to execution of malicious scripts in the context of the affected web application. However, the vendor regards this as an edge case and the CVSS score rates it as medium severity.
Mitigation Recommendations
Upgrade DOMPurify to version 3.4.0 or later, where this issue is fixed. No other official remediation or temporary fixes are documented. Patch status is confirmed by the vendor advisory indicating 3.4.0 as the fixed version.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-07-23T12:51:09.595Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a6215a29c2644c7f82072f5
Added to database: 07/23/2026, 13:22:42 UTC
Last enriched: 07/30/2026, 22:32:55 UTC
Last updated: 09/05/2026, 10:52:11 UTC
Views: 86
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