Permissive List of Allowed Inputs Affecting express-xss-sanitizer package, versions >=1.2.0 <2.0.2
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published29 Mar 2026
- disclosed27 Mar 2026
- creditLissy93
Introduced: 27 Mar 2026
NewCVE-2026-33979 (opens in a new tab)How to fix?
Upgrade express-xss-sanitizer to version 2.0.2 or higher.
Overview
express-xss-sanitizer is an Express 4.x middleware which sanitizes user input data (in req.body, req.query, req.headers and req.params) to prevent Cross Site Scripting (XSS) attack.
Affected versions of this package are vulnerable to Permissive List of Allowed Inputs through the initializeOptions function in lib/sanitize.js. An attacker can inject unintended HTML and XSS payloads by supplying content expected to be fully stripped when allowedTags or allowedAttributes are empty, causing a fallback to sanitize-html defaults instead of enforcing a deny-all configuration.
Notes
- The vulnerable behavior affects applications using
express-xss-sanitizerto sanitize untrusted input from request data such asreq.body,req.query,req.headers, orreq.params.