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5.7
Craft CMS: Attacker Can Fake Entry Authorship
CVE-2026-28781
GHSA-2xfc-g69j-x2mp
Summary
An attacker with the 'Create Entries' permission can manipulate the author of a new entry, making it appear as though a more privileged user created it. This could be used to bypass review processes or post malicious content. To fix this, ensure that users with 'Create Entries' permission are not allowed to assign authorship to others.
What to do
- Update craftcms cms to version 5.9.0-beta.1.
- Update craftcms cms to version 4.17.0-beta.1.
Affected software
| Vendor | Product | Affected versions | Fix available |
|---|---|---|---|
| craftcms | cms | > 5.0.0-RC1 , <= 5.9.0-beta.1 | 5.9.0-beta.1 |
| craftcms | cms | > 4.0.0-RC1 , <= 4.17.0-beta.1 | 4.17.0-beta.1 |
| craftcms | craft_cms | > 4.0.0 , <= 4.17.0 | – |
| craftcms | craft_cms | > 5.0.0 , <= 5.9.0 | – |
| craftcms | craft_cms | 4.0.0 | – |
| craftcms | craft_cms | 4.0.0 | – |
| craftcms | craft_cms | 4.0.0 | – |
| craftcms | craft_cms | 4.0.0 | – |
| craftcms | craft_cms | 5.0.0 | – |
| craftcms | craft_cms | 5.0.0 | – |
Original title
Craft CMS: Entries Authorship Spoofing via Mass Assignment
Original description
## 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 to the body params: `&authorIds[]=<Victim_ID>`
1. Forward the request
1. Log in as an admin / as with the victim account
1. Go to entries & Observe the newly created entry is listed and the author is the victim account, not the actual creator
## Impact
- A user can create entries that appear to belong to higher-privileged users, potentially bypassing review processes or gaining trust based on false authorship.
- An attacker could post malicious or inappropriate content attributed to an administrator or other trusted users.
## Resources
https://github.com/craftcms/cms/commit/c6dcbdffaf6ab3ffe77d317336684d83699f4542
https://github.com/craftcms/cms/commit/830b403870cd784b47ae42a3f5a16e7ac2d7f5a8
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 to the body params: `&authorIds[]=<Victim_ID>`
1. Forward the request
1. Log in as an admin / as with the victim account
1. Go to entries & Observe the newly created entry is listed and the author is the victim account, not the actual creator
## Impact
- A user can create entries that appear to belong to higher-privileged users, potentially bypassing review processes or gaining trust based on false authorship.
- An attacker could post malicious or inappropriate content attributed to an administrator or other trusted users.
## Resources
https://github.com/craftcms/cms/commit/c6dcbdffaf6ab3ffe77d317336684d83699f4542
https://github.com/craftcms/cms/commit/830b403870cd784b47ae42a3f5a16e7ac2d7f5a8
nvd CVSS3.1
6.5
nvd CVSS4.0
7.1
Vulnerability type
CWE-639
Authorization Bypass Through User-Controlled Key
CWE-915
- https://github.com/craftcms/cms/commit/c6dcbdffaf6ab3ffe77d317336684d83699f4542 Patch
- https://github.com/craftcms/cms/security/advisories/GHSA-2xfc-g69j-x2mp Exploit Patch Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-28781
- https://github.com/advisories/GHSA-2xfc-g69j-x2mp
- https://github.com/craftcms/cms/commit/830b403870cd784b47ae42a3f5a16e7ac2d7f5a8 Patch
Published: 3 Mar 2026 · Updated: 13 Mar 2026 · First seen: 6 Mar 2026