Craft CMS: Entries Authorship Spoofing via Mass Assignment

Exploitation

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

CVSS 4.0

5.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P · score source

EPSS

• CVE-2026-28781: 0.39% estimated exploitation activity in the next 30 days; percentile 32.93 (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.

Description The entry creation process allows for Mass Assignment of the authorId attribute. A user with "Create Entries" permission can inject the authorIds[] (or authorId) parameter into the POST request, which the backend processes without verifying if the current user is authorized to assign authorship to others. Normally, this field is not present in the request for users without the necessary permissions. By manually adding this parameter, an attacker can attribute the new entry to any user, including Admins. This effectively "spoofs" the authorship. Proof of Concept Prerequisites - A user account with "Create Entries" permission for a section. - Victim's account ID (e.g., 1 for the default Admin). Steps to Reproduce 1. Log in as the attacker 1. Navigate to the "Entries" section and click "New Entry" 1. Fill in the required fields 1. Enable a proxy tool (e.g., Burp Suite) to intercept requests 1. Click "Save" & Intercept the request 1. In the request body, add a new parameter…

Published by the source

3 Mar 2026, 21:00 UTC

Last modified by the source

4 Mar 2026, 18:39 UTC

Source last checked

26 Oct 2026, 14:38 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-2xfc-g69j-x2mp

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# Patch Next advisory brief: CVE-2026-28781

Advisory: Craft CMS: Entries Authorship Spoofing via Mass Assignment
IDs: CVE-2026-28781, GHSA-2xfc-g69j-x2mp
Record: https://patchnext.com/advisories/cve-2026-28781 (revision 1, source checked 26 Oct 2026, 14:38 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: craftcms/cms 5.9.0-beta.1, 4.17.0-beta.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist craftcms/cms: affected >= 5.0.0-RC1, < 5.9.0-beta.1; >= 4.0.0-RC1, < 4.17.0-beta.1; fixed in 5.9.0-beta.1, 4.17.0-beta.1

## Suggested inspection (read-only)
- Packagist craftcms/cms: 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 craftcms/cms.
- 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-2xfc-g69j-x2mp (GitHub-reviewed advisory GHSA-2xfc-g69j-x2mp lists affected ranges: Packagist craftcms/cms >=5.0.0-RC1 =4.0.0-RC1 <4.17.0-beta.1)

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