CVE-2026-33394 in Discourse
Summary
by MITRE • 03/20/2026
Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the Post Edits admin report (/admin/reports/post_edits) leaked the first 40 characters of raw post content from private messages and secure categories to moderators who shouldn't have access. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. No known workarounds are available.
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Analysis
by VulDB Data Team • 03/25/2026
The vulnerability identified as CVE-2026-33394 affects Discourse, an open-source discussion platform that serves as a collaborative forum system for communities and organizations. This security flaw represents a critical information disclosure issue that undermines the platform's access control mechanisms and data protection policies. The vulnerability specifically targets the Post Edits admin report functionality, which is designed to track and display modifications made to forum posts. Prior to the patched versions, this administrative feature failed to properly enforce access controls, creating a scenario where sensitive information could be exposed to unauthorized users.
The technical flaw manifests in the improper handling of access control validation within the Post Edits report module. When moderators accessed the /admin/reports/post_edits endpoint, the system leaked the first 40 characters of raw post content from private messages and secure categories. This represents a clear violation of the principle of least privilege and demonstrates a failure in the platform's data classification and access control implementation. The vulnerability essentially allows unauthorized users to gain partial visibility into content that should remain restricted to specific user groups or administrators.
The operational impact of this vulnerability extends beyond simple data exposure, as it fundamentally compromises the security posture of Discourse installations. Moderators who should only have access to public post modifications can now potentially access sensitive information from private communications and restricted categories. This creates a significant risk for organizations that rely on Discourse for internal communications, customer support systems, or any environment where confidentiality is paramount. The leaked information, while limited to the first 40 characters, could still provide context clues that might be valuable for social engineering attacks or to understand the nature of sensitive discussions.
From a cybersecurity perspective, this vulnerability aligns with CWE-200, which addresses "Information Exposure," and represents a classic case of inadequate access control implementation. The issue also maps to ATT&CK technique T1078.004, which covers "Valid Accounts: Cloud Accounts," as it exploits the legitimate access rights of moderators to gain unauthorized information access. The lack of available workarounds means that organizations cannot implement temporary mitigations while waiting for patches, making immediate upgrades to the affected versions critical for maintaining security.
The patch implemented in versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 addresses the core access control flaw by ensuring that the Post Edits report properly validates user permissions before displaying content. This fix likely involves strengthening the authorization checks within the reporting module to prevent access to private message content and secure category posts. Organizations using Discourse should prioritize updating their installations to these patched versions to eliminate the risk of unauthorized information disclosure. The vulnerability serves as a reminder of the critical importance of thorough access control testing and validation in web applications, particularly those handling sensitive communications and user data.