{"id":"CVE-2026-91134","title":"Discourse is an open-source discussion platform","summary":"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 conta…","severity":"medium","cvss":5.4,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N","cwe":["CWE-20"],"vendor":"discourse","product":"discourse","affected":["discourse < 2026.8.0","discourse >= 2026.7.0-latest, < 2026.7.2","discourse >= 2026.6.0-latest, < 2026.6.3","discourse >= 2026.1.0-latest, < 2026.1.8"],"published":"2026-09-24","updated":"2026-09-24","sourceUpdated":"2026-09-24T17:17:09.220","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-91134","references":[{"url":"https://github.com/discourse/discourse/commit/0a8015e6c7a5079981843721494d30c9a91f5415","label":"security-advisories@github.com"},{"url":"https://github.com/discourse/discourse/commit/1304b0c04f87534053b0d574ae5a9b9ba13dd590","label":"security-advisories@github.com"},{"url":"https://github.com/discourse/discourse/commit/bac7dd1201911851462483271b4567246fa1309d","label":"security-advisories@github.com"},{"url":"https://github.com/discourse/discourse/commit/fed3a58c48412ce7207b72a4629ddbc44482cd64","label":"security-advisories@github.com"},{"url":"https://github.com/discourse/discourse/pull/42882","label":"security-advisories@github.com"},{"url":"https://github.com/discourse/discourse/security/advisories/GHSA-54vw-chv3-wjpv","label":"security-advisories@github.com"}],"tags":["nvd","cve.org"],"ingestedAt":"2026-09-24T17:48:30.387Z","slug":"CVE-2026-91134","body":"## Overview\n\nDiscourse 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":29.7,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}