{"id":"CVE-2026-91134","aliases":["BIT-discourse-2026-91134","EUVD-2026-86298","GHSA-54vw-chv3-wjpv"],"status":"published","title":"Discourse: Block post iframes whose encoded userinfo bypasses the allowed_iframes allowlist","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.","severity":{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00216,"percentile":0.12114,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-20"],"published":"2026-09-24T16:51:34Z","modified":"2026-10-28T02:31:02Z","fixes":[{"ecosystem":"Bitnami","package":"discourse","fixed_in":["2026.8.0"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Bitnami","package":"discourse","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2026.8.0"}]}]}],"products":[{"vendor":"discourse","product":"discourse"}],"references":[{"url":"https://github.com/discourse/discourse/security/advisories/GHSA-54vw-chv3-wjpv","tags":["x_refsource_CONFIRM","web","advisory"]},{"url":"https://github.com/discourse/discourse/pull/42882","tags":["x_refsource_MISC","web","fix"]},{"url":"https://github.com/discourse/discourse/commit/0a8015e6c7a5079981843721494d30c9a91f5415","tags":["x_refsource_MISC","web","fix"]},{"url":"https://github.com/discourse/discourse/commit/1304b0c04f87534053b0d574ae5a9b9ba13dd590","tags":["x_refsource_MISC","web","fix"]},{"url":"https://github.com/discourse/discourse/commit/bac7dd1201911851462483271b4567246fa1309d","tags":["x_refsource_MISC","web","fix"]},{"url":"https://github.com/discourse/discourse/commit/fed3a58c48412ce7207b72a4629ddbc44482cd64","tags":["x_refsource_MISC","web","fix"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-91134","tags":["web","advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/91xxx/CVE-2026-91134.json","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-91134","title":"Discourse: Block post iframes whose encoded userinfo bypasses the allowed_iframes allowlist","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.","status":"published","published":"2026-09-24T16:51:34.057Z","modified":"2026-09-29T02:56:30.376Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T14:19:52.773089Z"}],"euvd":[{"id":"EUVD-2026-86298","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.","status":"published","published":"2026-09-24T16:51:34Z","modified":"2026-09-29T02:56:30Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T17:27:52.759804Z"}],"nvd":[{"id":"CVE-2026-91134","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.","status":"published","published":"2026-09-24T17:17:09.08Z","modified":"2026-09-29T03:17:21.58Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T14:12:51.036099Z"}],"osv":[{"id":"CVE-2026-91134","title":"Discourse: Block post iframes whose encoded userinfo bypasses the allowed_iframes allowlist","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.","status":"published","published":"2026-09-24T16:51:34.057Z","modified":"2026-10-28T02:31:02.064565463Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T15:45:20.269367Z"},{"id":"BIT-discourse-2026-91134","title":"Discourse: Block post iframes whose encoded userinfo bypasses the allowed_iframes allowlist","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.","status":"published","published":"2026-10-01T09:29:34.915Z","modified":"2026-10-01T10:10:46.224904094Z","updated_at":"2026-11-02T15:28:29.152062Z"}]}}