CVE-2026-91134 | BDVDB-2026-378708 Detail
discoursediscourse
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.
Impact#
Per CVSS v3.1: confidentiality impact low, integrity impact low, availability impact none. Attack vector: network.
Weaknesses#
- CWE-20 Improper Input Validation
References#
- https://github.com/discourse/discourse/security/advisories/GHSA-54vw-chv3-wjpv
- https://github.com/discourse/discourse/pull/42882
- 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
Exploit#
No public exploit known
History#
- Version 1Record published in the CVE List.
- Version 2Most recent update recorded in the CVE List.