GHSA-CJ63-JHHR-WCXV

Vulnerability from github – Published: 2026-04-03 03:45 – Updated: 2026-05-29 21:46
VLAI
Summary
DOMPurify USE_PROFILES prototype pollution allows event handlers
Details

Summary

When USE_PROFILES is enabled, DOMPurify rebuilds ALLOWED_ATTR as a plain array before populating it with the requested allowlists. Because the sanitizer still looks up attributes via ALLOWED_ATTR[lcName], any Array.prototype property that is polluted also counts as an allowlisted attribute. An attacker who can set Array.prototype.onclick = true (or a runtime already subject to prototype pollution) can thus force DOMPurify to keep event handlers such as onclick even when they are normally forbidden. The provided PoC sanitizes <img onclick=...> with USE_PROFILES and adds the sanitized output to the DOM; the polluted prototype allows the event handler to survive and execute, turning what should be a blocklist into a silent XSS vector.

Impact

Prototype pollution makes DOMPurify accept dangerous event handler attributes, which bypasses the sanitizer and results in DOM-based XSS once the sanitized markup is rendered.

Credits

Identified by Cantina’s Apex (https://www.cantina.security).

Severity
5.3 (Medium)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N
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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.3.1"
      },
      "package": {
        "ecosystem": "npm",
        "name": "dompurify"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.3.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-1321"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-03T03:45:08Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Summary\nWhen `USE_PROFILES` is enabled, DOMPurify rebuilds `ALLOWED_ATTR` as a plain array before populating it with the requested allowlists. Because the sanitizer still looks up attributes via `ALLOWED_ATTR[lcName]`, any `Array.prototype` property that is polluted also counts as an allowlisted attribute. An attacker who can set `Array.prototype.onclick = true` (or a runtime already subject to prototype pollution) can thus force DOMPurify to keep event handlers such as `onclick` even when they are normally forbidden. The provided PoC sanitizes `\u003cimg onclick=...\u003e` with `USE_PROFILES` and adds the sanitized output to the DOM; the polluted prototype allows the event handler to survive and execute, turning what should be a blocklist into a silent XSS vector.\n\n## Impact\nPrototype pollution makes DOMPurify accept dangerous event handler attributes, which bypasses the sanitizer and results in DOM-based XSS once the sanitized markup is rendered.\n\n## Credits\nIdentified by Cantina\u2019s Apex (https://www.cantina.security).",
  "id": "GHSA-cj63-jhhr-wcxv",
  "modified": "2026-05-29T21:46:57Z",
  "published": "2026-04-03T03:45:08Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/cure53/DOMPurify/security/advisories/GHSA-cj63-jhhr-wcxv"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/cure53/DOMPurify"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cure53/DOMPurify/releases/tag/3.3.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "DOMPurify USE_PROFILES prototype pollution allows event handlers"
}


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