CVE-2026-91134
MEDIUM
5,4
Source: [email protected]
Attack Vector: network
Attack Complexity: low
Privileges Required: low
User Interaction: none
Scope: unchanged
Confidentiality: low
Integrity: low
Availability: none
Description
AI Translation Available
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.
20
Improper Input Validation
StableCommon Consequences
Security Scopes Affected:
Availability
Confidentiality
Integrity
Potential Impacts:
Dos: Crash, Exit, Or Restart
Dos: Resource Consumption (Cpu)
Dos: Resource Consumption (Memory)
Read Memory
Read Files Or Directories
Modify Memory
Execute Unauthorized Code Or Commands
Applicable Platforms
Technologies:
AI/ML
https://github.com/discourse/discourse/commit/0a8015e6c7a5079981843721494d30c9a…
https://github.com/discourse/discourse/commit/1304b0c04f87534053b0d574ae5a9b9ba…
https://github.com/discourse/discourse/commit/bac7dd1201911851462483271b4567246…
https://github.com/discourse/discourse/commit/fed3a58c48412ce7207b72a4629ddbc44…
https://github.com/discourse/discourse/pull/42882
https://github.com/discourse/discourse/security/advisories/GHSA-54vw-chv3-wjpv