{"id":"BIT-discourse-2026-91134","summary":"Discourse: Block post iframes whose encoded userinfo bypasses the allowed_iframes allowlist","details":"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.","aliases":["CVE-2026-91134","GHSA-54vw-chv3-wjpv"],"modified":"2026-10-01T10:10:46.224904094Z","published":"2026-10-01T09:29:34.915Z","database_specific":{"cpes":["cpe:2.3:a:discourse:discourse:*:*:*:*:stable:*:*:*","cpe:2.3:a:discourse:discourse:*:*:*:*:beta:*:*:*"],"severity":"Medium"},"references":[{"type":"WEB","url":"https://github.com/discourse/discourse/commit/0a8015e6c7a5079981843721494d30c9a91f5415"},{"type":"WEB","url":"https://github.com/discourse/discourse/commit/1304b0c04f87534053b0d574ae5a9b9ba13dd590"},{"type":"WEB","url":"https://github.com/discourse/discourse/commit/bac7dd1201911851462483271b4567246fa1309d"},{"type":"WEB","url":"https://github.com/discourse/discourse/commit/fed3a58c48412ce7207b72a4629ddbc44482cd64"},{"type":"WEB","url":"https://github.com/discourse/discourse/pull/42882"},{"type":"WEB","url":"https://github.com/discourse/discourse/security/advisories/GHSA-54vw-chv3-wjpv"},{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-91134"}],"affected":[{"package":{"name":"discourse","ecosystem":"Bitnami","purl":"pkg:bitnami/discourse"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2026.8.0"}]}],"database_specific":{"source":"https://github.com/bitnami/vulndb/tree/main/data/discourse/BIT-discourse-2026-91134.json"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N"}]}],"schema_version":"1.9.0"}