CVE-2026-26058

Zulip is an open-source team collaboration tool. From 11.0 until 12.2, organizations with web-public channels enabled exposed the GET /json/users endpoint to logged-out spectators, and a missing access-control check allowed include_custom_profile_fields=true to return every user's custom profile field values in addition to the documented limited directory data. This exposed those custom profile field values to unauthenticated visitors. This issue is fixed in version 12.2.

Zulip is an open-source team collaboration tool. From 8.0 until 12.2, in organizations where the 'Who can view all other users in the organization' setting restricted guests from viewing other users, saving or editing a direct message draft did not verify that the sender could access the draft recipients. A guest could thereby gain access to otherwise restricted users' profile information without sending a message. Organizations that did not restrict guest access were unaffected. This issue is fixed in version 12.2.

In Zulip before version 11.6, even after disabling spectator access, attachments from web-public streams remained anonymously accessible. Additionally, the /users/me/<stream_id>/topics endpoint remained reachable anonymously, allowing retrieval of topic history for those streams.