CVE-2026-72724

Summary

Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, plugins/chat/lib/chat/onebox_handler.rb resolves Chat::Thread by route thread_id independently of the route channel_id before checking whether the user can preview the selected chat channel. An authenticated user can pair a public channel ID with a private thread ID in a /onebox.json request and obtain private thread message content. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.

Affected Software

VendorProductVersion RangeStatus
discoursediscourse< 2026.1.6affected
discoursediscourse>= 2026.5.0-latest, < 2026.5.2affected
discoursediscourse>= 2026.6.0-latest, < 2026.6.1affected
discoursediscourse>= 2026.7.0-latest, < 2026.7.0affected

Weaknesses

  • CWE-639: CWE-639: Authorization Bypass Through User-Controlled Key

References