CVE-2026-72724
MediumCVSS 4.3Exploitation Probability (EPSS)
Low risk25th percentile - higher than 25% of all known CVEs
Summary
Discourse prior to versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0 in 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.
Risk Assessment
Disclosure of private chat message content may compromise communication confidentiality and lead to leakage of sensitive information.
Recommendation
Update Discourse to version 2026.1.6, 2026.5.2, 2026.6.1, or 2026.7.0.
Original NVD description (English source)
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.