Flarum post mentions can be used to read any post on the forum without access control

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.7 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

EPSS

• CVE-2023-22487: 0.69% estimated exploitation activity in the next 30 days; percentile 52.63 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Using the mentions feature provided by the flarum/mentions extension, users can mention any post ID on the forum with the special @"<username"#p<id syntax. The following behavior never changes no matter if the actor should be able to read the mentioned post or not: A URL to the mentioned post is inserted into the actor post HTML, leaking its discussion ID and post number. The mentionsPosts relationship included in the POST /api/posts and PATCH /api/posts/<id JSON responses leaks the full JSON:API payload of all mentioned posts without any access control. This includes the content, date, number and attributes added by other extensions. An attacker only needs the ability to create new posts on the forum to exploit the vulnerability. This works even if new posts require approval. If they have the ability to edit posts, the attack can be performed even more discreetly by using a single post to scan any size of database and hiding the attack post content afterward. Impact The attack…

Published by the source

10 Jan 2023, 22:19 UTC

Last modified by the source

27 Jan 2023, 05:05 UTC

Source last checked

26 Oct 2026, 14:00 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-22m9-m3ww-53h3

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# Patch Next advisory brief: CVE-2023-22487

Advisory: Flarum post mentions can be used to read any post on the forum without access control
IDs: CVE-2023-22487, GHSA-22m9-m3ww-53h3
Record: https://patchnext.com/advisories/cve-2023-22487 (revision 1, source checked 26 Oct 2026, 14:00 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: flarum/mentions 1.6.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist flarum/mentions: affected < 1.6.3; fixed in 1.6.3

## Suggested inspection (read-only)
- Packagist flarum/mentions: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on flarum/mentions.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-22m9-m3ww-53h3 (GitHub-reviewed advisory GHSA-22m9-m3ww-53h3 lists affected ranges: Packagist flarum/mentions >=0 <1.6.3)

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