--- title: "CVE-2026-91159: Discourse - Stored XSS" description: "Discourse < 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9 contains a stored XSS caused by trusted processing of attacker-controlled HTML fragments with allowlisted iframes in oEmbed, letting users with posting permission inject misleading UI, exploit requires posting account and control of allowlisted iframe source." url: https://panop.io/threat-heartbeat/CVE-2026-91159/ --- # CVE-2026-91159 Discourse - Stored XSS Discourse < 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9 contains a stored XSS caused by trusted processing of attacker-controlled HTML fragments with allowlisted iframes in oEmbed, letting users with posting permission inject misleading UI, exploit requires posting account and control of allowlisted iframe source. CVSS base score 7.7 /10 High CISA KEV Not listed Public exploit Proof of concept available Authentication Required [View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-91159) ## Details Type Stored XSS Impact Stored XSS CVSS vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N Published 14 October 2026 Updated 15 October 2026 Weakness [CWE-79](https://cwe.mitre.org/data/definitions/79.html) ## Vendor fix Update to versions 2026.9.0, 2026.8.1, 2026.7.3, or 2026.1.9. Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them. ## References - [https://nvd.nist.gov/vuln/detail/CVE-2026-91159](https://nvd.nist.gov/vuln/detail/CVE-2026-91159) - [https://github.com/discourse/discourse/commit/3fc2bad6cdca47b00958330d1ee612aa141b039a](https://github.com/discourse/discourse/commit/3fc2bad6cdca47b00958330d1ee612aa141b039a) - [https://github.com/discourse/discourse/commit/dde8bc4fb6200139f5eff7e100b0f3e829d37ab3](https://github.com/discourse/discourse/commit/dde8bc4fb6200139f5eff7e100b0f3e829d37ab3) - [https://github.com/discourse/discourse/commit/ed6f83f123d1a4c6c6c7e64c8a2233e3cb6a28d7](https://github.com/discourse/discourse/commit/ed6f83f123d1a4c6c6c7e64c8a2233e3cb6a28d7) - [https://github.com/discourse/discourse/security/advisories/GHSA-f9jx-vv33-4282](https://github.com/discourse/discourse/security/advisories/GHSA-f9jx-vv33-4282) - [https://github.com/discourse/discourse/commit/0953b31f5c2949d7d6ab5f6dc4c5e2f1b8bf0b22](https://github.com/discourse/discourse/commit/0953b31f5c2949d7d6ab5f6dc4c5e2f1b8bf0b22) [← All CVEs](https://panop.io/threat-heartbeat/) ## What this record can't tell you - Whether you run the affected software, and where - Whether an attacker can actually reach and exploit it - The misconfigurations that never get a CVE number - What it would cost the business, ranked into what to fix first Panop answers these inside your environment, for this CVE and every other finding. [Book a demo](https://panop.io/demo)