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

> Attackers can read hidden post revisions by enumerating version numbers due to missing authorization checks on the posts endpoint.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Mar 2026
- **Updated:** 20 Mar 2026
- **Also known as:** BIT-discourse-2026-27454, GHSA-fq69-f929-wp96

## What is CVE-2026-27454?

CVE-2026-27454 is a medium-severity missing authorization vulnerability in Discourse Discourse, published on 19 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### 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.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-27454?

1 open source package ship an affected version, including discourse. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `discourse` | Bitnami | From 2026.1.0 | 2026.1.2, 2026.2.1, 2026.3.0 |

Products: Discourse Discourse.

## How do I fix CVE-2026-27454?

Upgrade discourse to a fixed version for your release line: 2026.1.2, 2026.2.1 or 2026.3.0.

## Is CVE-2026-27454 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27454 exists.

Public exploit code:

- Discourse <=2026.2.0 - Hidden Post Revision Disclosure via revert_to Authorization Bypass (nuclei): http/cves/2026/CVE-2026-27454.yaml

## Other vulnerabilities in Discourse Discourse

- [CVE-2021-41163](https://insights.sbomify.com/CVE-2021-41163/): RCE via malicious SNS subscription payload (critical 10.0)
- [CVE-2022-36066](https://insights.sbomify.com/CVE-2022-36066/): Discourse vulnerable to RCE via admins uploading maliciously zipped file (critical 9.1)
- [CVE-2022-39356](https://insights.sbomify.com/CVE-2022-39356/): Discourse user account takeover via email and invite link (high 8.9)
- [CVE-2023-22468](https://insights.sbomify.com/CVE-2023-22468/): Discourse vulnerable to Cross-site Scripting in local oneboxes (high 8.8)
- [CVE-2026-27934](https://insights.sbomify.com/CVE-2026-27934/): Discourse leaks private topic title and post excerpt via user action API endpoint (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27454 and fix it if it is affected.

What it is: CVE-2026-27454 is a medium-severity missing authorization vulnerability in Discourse Discourse, published on 19 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27454 exists.

Affected packages and fixed versions:
- discourse (Bitnami): affected from 2026.1.0; fixed in 2026.1.2, 2026.2.1, 2026.3.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-27454/ (Markdown: https://insights.sbomify.com/CVE-2026-27454/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27454
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27454
- OSV: https://osv.dev/vulnerability/CVE-2026-27454

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27454/
Summaries are generated and may contain mistakes; the official description above is the record.