Discourse is an open-source discussion platform. In versions prior to 2026.1.4, 2026.3.1, 2026.4.1 and 2026.5.0-latest.1, a vulnerability in the discourse-subscriptions plugin allows users to gain access to subscription-gated groups without completing payment. This issue has been fixed in versions 2026.1.4, 2026.3.1, 2026.4.1 and 2026.5.0-latest.1.

Discourse is an open-source discussion platform. In versions prior to 2026.1.4, 2026.3.1, 2026.4.1 and 2026.5.0-latest.1, an authenticated user on a Discourse instance with the form templates feature enabled can read the name and structured content of form templates that are intended exclusively for categories they are not authorized to access. Impact is limited to disclosure of site configuration metadata. This issue has been fixed in versions 2026.1.4, 2026.3.1, 2026.4.1 and 2026.5.0-latest.1.

Discourse is an open-source discussion platform. In versions prior to 2026.1.4, 2026.3.1, 2026.4.1 and 2026.5.0-latest.1, outdated cached AI summaries can leak removed content to anonymous and unprivileged users who cannot regenerate summaries. This issue has been fixed in versions 2026.1.4, 2026.3.1, 2026.4.1 and 2026.5.0-latest.1. To work around this issue, restrict summary generation by tightening the allowed groups on the summarization Personas.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, staged user custom fields and username are exposed on public invite pages without email verification. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, an authorization bypass vulnerability allows unauthenticated or unauthorized users to view hidden (staff-only) tags and its associated data. All Discourse instances with tagging enabled and staff-only tag groups configured are impacted. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, an authenticated moderator-level user could retrieve post content, topic titles, and usernames from categories they were not authorized to view. Insufficient access controls on a sentiment analytics endpoint allowed category permission boundaries to be bypassed. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, an authorization bypass in the Category Chatables Controller show action allowed moderators to get information on hidden groups names and user count. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, the group email settings test endpoint could be used to make the server initiate outbound connections to arbitrary hosts and ports. This could allow probing of internal network infrastructure. The endpoint was accessible to non-staff group owners. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, a user may be able to purchase a lower tier subscription but grant themselves the benefits that comes along with a higher tier subscription. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, the discourse-subscriptions plugin leaks stripe API keys across sites in a multisite cluster resulting in the potential for stripe related information to be leaked across sites within the same multisite cluster. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, an authenticated user can obtain shared draft topic titles by sending an inline onebox request with a category_id parameter matching the shared drafts category. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, non-staff users could access read receipt information for staff-only posts they weren't supposed to see. No post content was exposed, only metadata about who read the post and when. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, users who lost access to a topic (e.g., removed from a private category group) could still interact with polls in that topic, including voting and toggling poll status. No content was exposed, but users could modify poll state in topics they should no longer have access to. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, there is possible channel membership inference from chat user search without authorization. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, category group moderators could perform privileged actions on topics inside private categories they did not have read access to. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, when the hidden prioritize_full_name_in_ux site setting is enabled (defaults to false, requires console access to change), user and group display names are rendered without HTML escaping in several assignment-related UI paths. This allows users with assign permission to inject arbitrary HTML/JavaScript that executes in the browser of any user viewing an affected topic. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, updating a category description via API is not sanitizing the description string, which can lead to XSS attacks. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, an attacker with the ability to create shared AI conversations could inject arbitrary HTML and JavaScript via crafted conversation titles. This payload would execute in the browser of any user viewing the onebox preview, potentially allowing session hijacking or unauthorized actions on behalf of the victim. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, moderators could export CSV data for admin-restricted reports, bypassing the report visibility restrictions. This could expose sensitive operational data intended only for admins. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, the enter action in StaticController reads the sso_destination_url cookie and redirects to it with allow_other_host: true without validating the destination URL. While this cookie is normally set during legitimate DiscourseConnect Provider flows with cryptographically validated SSO payloads, cookies are client-controlled and can be set by attackers. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, a non-staff user with elevated group membership could access deleted posts belonging to any user due to an overly broad authorization check on the deleted posts index endpoint. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. No known workarounds are available.

Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, an unauthenticated attacker can cause a legitimate Discourse authorization page to display an attacker-controlled domain, facilitating social engineering attacks against users. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. No known workarounds are available.

Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, users with tag-editing permissions could edit and create synonyms for tags hidden in restricted tag groups, even if they lacked visibility into those tags. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. No known workarounds are available.

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.

Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, an attacker can grant access to a private message topic through invites even after they lose access to that PM. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. No known workarounds are available.