{"cve":"CVE-2026-91134","nvd":{"published":"2026-09-24T17:17:09.080","modified":"2026-09-29T03:17:21.580","status":"Deferred","description":"Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the Discourse post sanitizer allowed a stored cross-origin iframe to bypass the allowed_iframes prefix policy when the iframe src contained encoded userinfo. The sanitizer validated a decoded form differently from the stored iframe src, allowing the browser to interpret an attacker-controlled host while the allowlist check accepted the encoded URL as an allowed prefix. An authenticated user with posting privileges could persist the iframe in a post and cause attacker-controlled cross-origin content to be rendered. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N","score":5.4},"cwes":["CWE-20"],"references":["https://github.com/discourse/discourse/commit/0a8015e6c7a5079981843721494d30c9a91f5415","https://github.com/discourse/discourse/commit/1304b0c04f87534053b0d574ae5a9b9ba13dd590","https://github.com/discourse/discourse/commit/bac7dd1201911851462483271b4567246fa1309d","https://github.com/discourse/discourse/commit/fed3a58c48412ce7207b72a4629ddbc44482cd64","https://github.com/discourse/discourse/pull/42882"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:56:02.509636177+00:00"},"epss":{"cve":"CVE-2026-91134","score":0.00216,"percentile":0.12029,"date":"2026-10-31"},"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."]}