CVE-2026-28227 in Discourse
Summary
by MITRE • 02/27/2026
Discourse is an open source discussion platform. Prior to versions 2025.12.2, 2026.1.1, and 2026.2.0, TL4 users can publish topics into staff-only categories via the `publish_to_category` topic timer, bypassing authorization checks. Versions 2025.12.2, 2026.1.1, and 2026.2.0 patch the issue. No known workarounds are available.
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Analysis
by VulDB Data Team • 03/03/2026
The vulnerability described in CVE-2026-28227 affects Discourse, an open source discussion platform that serves as a collaborative forum system for communities and organizations. This security flaw represents a significant authorization bypass issue that undermines the platform's access control mechanisms, particularly within staff-only categories where sensitive discussions are intended to remain restricted to authorized personnel only. The vulnerability specifically targets users with the TL4 user level, which typically represents a higher tier of user privileges but should not grant access to restricted administrative areas of the platform.
The technical flaw manifests through the `publish_to_category` topic timer functionality, which is designed to schedule topic publication to specific categories at predetermined times. This mechanism fails to properly validate user permissions when attempting to publish topics into staff-only categories, allowing TL4 users to circumvent the normal authorization checks that should prevent such actions. The vulnerability exists in the permission validation logic within the topic timer implementation, where the system does not adequately verify whether the user has proper authorization to publish content into restricted category spaces. This represents a classic authorization bypass vulnerability that falls under CWE-285, which specifically addresses insufficient authorization checks within software systems.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it potentially allows unauthorized users to publish sensitive content into restricted areas of the discussion platform. This could result in exposure of confidential discussions, staff-only communications, or other restricted content that should remain inaccessible to standard users. The vulnerability affects a broad range of Discourse installations, as it was present in versions prior to the patched releases, meaning that organizations with older installations may have been unknowingly compromised. Attackers could exploit this vulnerability to gain unauthorized access to staff-only categories and potentially manipulate the content flow within these restricted areas, undermining the platform's security model and potentially exposing sensitive information.
Organizations using Discourse should immediately upgrade to versions 2025.12.2, 2026.1.1, or 2026.2.0 to remediate this vulnerability, as no known workarounds exist to address the issue without patching the software. The vulnerability aligns with ATT&CK technique T1078 which covers valid accounts and privilege escalation, as it allows users to perform actions they should not be authorized to perform through legitimate access channels. The lack of available workarounds means that organizations cannot implement temporary fixes while planning upgrades, making immediate patching essential for maintaining platform security and protecting sensitive information within staff-only categories. Security teams should also monitor for any unauthorized activity in staff-only categories following the patch deployment to ensure no exploitation occurred during the vulnerable period.