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OpenAdvisories
High · 8.2 CVE-2026-33979 EUVD-2026-16876GHSA-3843-rr4g-m8jq

Express XSS Sanitizer: allowedTags/allowedAttributes bypass leads to permissive sanitization (XSS risk)

Published Mar 27, 2026 · Updated Mar 31, 2026 · Assigned by GitHub_M

Description

Express XSS Sanitizer is Express 4.x and 5.x middleware which sanitizes user input data (in req.body, req.query, req.headers and req.params) to prevent Cross Site Scripting (XSS) attack. A vulnerability has been identified in versions prior to 2.0.2 where restrictive sanitization configurations are silently ignored. In version 2.0.2, the validation logic has been updated to respect explicitly provided empty configurations. Now, if allowedTags or allowedAttributes are provided (even if empty), they are passed directly to sanitize-html without being overridden.

Affected products

VendorProductAffectedFixed
AhmedAdelFahim express-xss-sanitizer < 2.0.2 —

Affected packages

EcosystemPackageAffectedFixedRecord
npm express-xss-sanitizer < 2.0.2 2.0.2 GHSA-3843-rr4g-m8jq

References