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

Quick assessment

Affected
discourse discourse
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Discourse是Discourse开源的一套开源的社区讨论平台。该平台包括社区、电子邮件和聊天室等功能。 Discourse 2026.3.0-latest.1之前版本、2026.2.1之前版本和2026.1.2之前版本存在安全漏洞，该漏洞源于请求/posts/:id.json?version=X时绕过帖子修订的授权检查，可能导致隐藏的修订被任意用户读取。

CVSS 5.3 · Medium EPSS 0.99% · P61

Public Exploits 1

Nuclei · 1 CVE-2026-27454.yaml [template]
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I. Basic Information for CVE-2026-27454

Vulnerability Information
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Vulnerability Title
Discourse has check revision visibility on posts endpoint
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制缺失
Source: CVE Program / CVE List V5
Vulnerability Title
Discourse 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Discourse是Discourse开源的一套开源的社区讨论平台。该平台包括社区、电子邮件和聊天室等功能。 Discourse 2026.3.0-latest.1之前版本、2026.2.1之前版本和2026.1.2之前版本存在安全漏洞，该漏洞源于请求/posts/:id.json?version=X时绕过帖子修订的授权检查，可能导致隐藏的修订被任意用户读取。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
discourse discourse >= 2026.1.0-latest, < 2026.1.2 -

II. Public POCs for CVE-2026-27454

# POC Description Source Link Shenlong Link
1 Discourse versions before 2026.1.2, 2026.2.1, and 2026.3.0-latest.1 contain an authorization bypass in PostsController#display_post. The controller calls post.revert_to(params[:version]) directly whenever a version query parameter is present, without checking whether the corresponding PostRevision is hidden or whether the caller has permission to view edit history. By requesting a post at its publicly known version number via GET /posts/:id.json?version=<public_version>, the next PostRevision's stored modifications are applied unconditionally. If staff have hidden that revision, its pre-edit content is returned to an unauthenticated caller. On patched installs the same request is rejected with 403 because guardian.ensure_can_see!(post_revision) is evaluated first. https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-27454.yaml POC Details
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III. Intelligence Information for CVE-2026-27454

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Patches & Fixes for CVE-2026-27454 (3)

Vendor Advisories for CVE-2026-27454 (1)

Same Patch Batch · discourse · 2026-03-19 · 17 CVEs total

CVE-2026-33355 6.5 MEDIUM Discourse filters whisper posts from private-posts feed
CVE-2026-33410 5.4 MEDIUM Discourse hardens chat DM channel creation and expansion
CVE-2026-33395 4.4 MEDIUM Discourse has stored click‑based XSS via Graphviz SVG javascript: links
CVE-2026-32099 4.3 MEDIUM Discourse prevents hidden profile data leak via user onebox
CVE-2026-33393 4.3 MEDIUM Discourse fixes loose hostname matching in spam host allowlist
CVE-2026-27166 4.1 MEDIUM Discourse vulnerable to HTML injection via prohibited iframe URLs
CVE-2026-33394 2.7 LOW Discourse leaks PM post edits to moderators
CVE-2026-33408 2.2 LOW Discourse has Improper Authorization in "Post Edits" Report For Moderators
CVE-2026-27491 Discourse has a bypass of official warnings messages by non-staff users
CVE-2026-27570 Discourse Vulnerable to Stored XSS via Shared AI Conversation Onebox
CVE-2026-27740 Discourse has Stored XSS in AI Triage Automation
CVE-2026-27934 Discourse leaks private topic title and post excerpt via user action API endpoint
CVE-2026-27935 Discourse leaks private topic metadata to non-authorized users
CVE-2026-27936 Discourse discloses restricted post-action counts to non-privileged users
CVE-2026-28282 Discourse vulnerable to group membership addition permission bypass via discourse-policy p
CVE-2026-29072 Discourse missing permission check for policy creation in discourse-policy

IV. Related Vulnerabilities

Same product: discourse
Same vendor: discourse
Same weakness: CWE-862

V. Comments for CVE-2026-27454

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