Description
Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, unauthenticated users can determine whether a specific user is a member of a private group by observing changes in directory results when using the `exclude_groups` parameter. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. As a workaround, disable public access to the user directory via Admin → Settings → hide user profiles from public.
Problem types
CWE-203: Observable Discrepancy
CWE-639: Authorization Bypass Through User-Controlled Key
CWE-862: Missing Authorization
Product status
>= 2026.2.0-latest, < 2026.2.1
= 2026.3.0-latest
References
github.com/...course/security/advisories/GHSA-r6rh-xvf5-r5f2