{"cve":"CVE-2026-91159","nvd":{"published":"2026-10-14T16:17:56.613","modified":"2026-10-20T02:17:13.347","status":"Deferred","description":"Discourse is an open-source discussion platform. Prior to 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9, oEmbed processing treated an entire attacker-controlled HTML fragment as trusted when the fragment contained an iframe whose source matched the configured allowlist. A user with posting permission who controlled a public webpage and its oEmbed response could combine an allowlisted iframe with unrelated sibling HTML or CSS, causing stored visual overlays or other styled content to appear in post content and enabling misleading or fraudulent user interfaces. Exploitation requires a posting account, control of the fetched webpage and oEmbed response, and an allowlisted iframe source. The issue affects content integrity but does not expose restricted data, disrupt availability, or require interaction with Discourse Content Security Policy. This issue is fixed in versions 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N","score":7.7},"cwes":["CWE-79"],"references":["https://github.com/discourse/discourse/commit/0953b31f5c2949d7d6ab5f6dc4c5e2f1b8bf0b22","https://github.com/discourse/discourse/commit/3fc2bad6cdca47b00958330d1ee612aa141b039a","https://github.com/discourse/discourse/commit/dde8bc4fb6200139f5eff7e100b0f3e829d37ab3","https://github.com/discourse/discourse/commit/ed6f83f123d1a4c6c6c7e64c8a2233e3cb6a28d7","https://github.com/discourse/discourse/security/advisories/GHSA-f9jx-vv33-4282"],"products":[],"source":"nvd","synced_at":"2026-10-21T03:56:58.798400159+00:00"},"epss":{"cve":"CVE-2026-91159","score":0.00417,"percentile":0.35702,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}