CVE-2026-91134 (GCVE-0-2026-91134)
Vulnerability from cvelistv5
Published
2026-09-24 16:51
Modified
2026-09-29 02:56
Severity ?
5.4 (Medium) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
CWE
  • CWE-20 - Improper Input Validation
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 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.
References
Impacted products
Vendor Product Version
discourse discourse Version: < 2026.8.0
Version: >= 2026.7.0-latest, < 2026.7.2
Version: >= 2026.6.0-latest, < 2026.6.3
Version: >= 2026.1.0-latest, < 2026.1.8
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