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Vulnerability · Published Mar 19, 2026 · Assigned by GitHub_M

CVE-2026-27454Discourse has check revision visibility on posts endpoint

Medium 5.3

In plain English

A medium-severity missing authorization in discourse from discourse. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.0% (higher than 62% of all known vulnerabilities). Ready-made attack tooling exists: Nuclei.

Severity (CVSS 3.1)5.3Medium
Exploit odds (30 days)1.0%top 37.7% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack tooling1Nuclei

Official description

Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, requesting /posts/:id.json?version=X bypassed authorization checks on post revisions. The display_post method called post.revert_to directly without verifying whether the revision was hidden or if the user had permission to view edit history. This meant hidden revisions (intentionally concealed by staff) could be read by any user by simply enumerating version numbers. Starting in versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, Discourse looks up the PostRevision and call guardian.ensure_can_see! before reverting, consistent with how the /posts/:id/revisions/:revision endpoint already authorizes access. No known workarounds are available.

Affected products (as reported)

VendorProductVersions
discourse discourse >= 2026.1.0-latest, < 2026.1.2>= 2026.2.0-latest, < 2026.2.1= 2026.3.0-latest

Weakness: CWE-862 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

References