CVE-2026-56381: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in craftcms cms
## Summary A stored XSS vulnerability exists in the User Permissions page. The User Group name is rendered without proper HTML escaping in the permissions section, allowing an attacker to execute arbitrary JavaScript when another user views or edits a user's permissions. > [!NOTE] > This is a separate vulnerability from the previously reported "[Stored XSS via User Group Name in User Settings Page](https://github.com/craftcms/cms/security/advisories/GHSA-2423-8xxj-wc3g)" and "[Multiple Stored XSS in User Group Edit Page](https://github.com/craftcms/cms/security/advisories/GHSA-vx7g-xw92-g4xj)". This affects a different sink: the individual user's permissions page. ## Proof of Concept ### Required Permissions - Admin access - `allowAdminChanges` is enabled in production, which is against our [security recommendations](https://craftcms.com/knowledge-base/securing-craft). ### Steps to Reproduce 1. Log in to the control panel as an admin 2. Navigate to **Settings → Users → User Groups** 3. Create or edit a user group and set the **Name** field to: ```html <img src=x onerror="alert('XSS')" hidden> ``` 4. Save the user group 5. Navigate to **Users** and edit any user (`/admin/users/{id}`) 6. Click on the **Permissions** tab 7. XSS executes ## Mitigation Sanitize user group names when rendering in the user permissions template. ## References https://github.com/craftcms/cms-ghsa-4mgv-366x-qxvx/pull/2
AI Analysis
Technical Summary
CVE-2026-56381 is a stored cross-site scripting vulnerability in Craft CMS 5.0.0-RC1. The issue occurs on the User Permissions page where user group names are not properly HTML-escaped before rendering. An attacker with administrative privileges can inject JavaScript code via the user group name field. This code executes in the context of other users who access the permissions page, potentially leading to script execution within their browsers. The vulnerability has a CVSS 4.6 (medium) score and no known exploits in the wild. No official patch or remediation level has been provided as of the published date.
Potential Impact
An attacker with admin privileges can inject arbitrary JavaScript code that executes in the browsers of other users who view or edit user permissions. This can lead to unauthorized actions performed on behalf of those users or theft of session information. The vulnerability requires high privileges (admin access) and user interaction (viewing/editing permissions). The overall impact is limited by these conditions but still poses a risk of cross-site scripting attacks within the administrative interface.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict admin access to trusted users only and avoid using user group names containing untrusted input. Monitor vendor channels for updates or patches addressing this vulnerability.
CVE-2026-56381: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in craftcms cms
Description
## Summary A stored XSS vulnerability exists in the User Permissions page. The User Group name is rendered without proper HTML escaping in the permissions section, allowing an attacker to execute arbitrary JavaScript when another user views or edits a user's permissions. > [!NOTE] > This is a separate vulnerability from the previously reported "[Stored XSS via User Group Name in User Settings Page](https://github.com/craftcms/cms/security/advisories/GHSA-2423-8xxj-wc3g)" and "[Multiple Stored XSS in User Group Edit Page](https://github.com/craftcms/cms/security/advisories/GHSA-vx7g-xw92-g4xj)". This affects a different sink: the individual user's permissions page. ## Proof of Concept ### Required Permissions - Admin access - `allowAdminChanges` is enabled in production, which is against our [security recommendations](https://craftcms.com/knowledge-base/securing-craft). ### Steps to Reproduce 1. Log in to the control panel as an admin 2. Navigate to **Settings → Users → User Groups** 3. Create or edit a user group and set the **Name** field to: ```html <img src=x onerror="alert('XSS')" hidden> ``` 4. Save the user group 5. Navigate to **Users** and edit any user (`/admin/users/{id}`) 6. Click on the **Permissions** tab 7. XSS executes ## Mitigation Sanitize user group names when rendering in the user permissions template. ## References https://github.com/craftcms/cms-ghsa-4mgv-366x-qxvx/pull/2
CVSS v4.0
Score 4.6medium
Affected software
craftcms
cms
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-56381 is a stored cross-site scripting vulnerability in Craft CMS 5.0.0-RC1. The issue occurs on the User Permissions page where user group names are not properly HTML-escaped before rendering. An attacker with administrative privileges can inject JavaScript code via the user group name field. This code executes in the context of other users who access the permissions page, potentially leading to script execution within their browsers. The vulnerability has a CVSS 4.6 (medium) score and no known exploits in the wild. No official patch or remediation level has been provided as of the published date.
Potential Impact
An attacker with admin privileges can inject arbitrary JavaScript code that executes in the browsers of other users who view or edit user permissions. This can lead to unauthorized actions performed on behalf of those users or theft of session information. The vulnerability requires high privileges (admin access) and user interaction (viewing/editing permissions). The overall impact is limited by these conditions but still poses a risk of cross-site scripting attacks within the administrative interface.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict admin access to trusted users only and avoid using user group names containing untrusted input. Monitor vendor channels for updates or patches addressing this vulnerability.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-06-21T02:05:47.495Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a37ed4baaf2dc2701b22757
Added to database: 06/21/2026, 13:55:23 UTC
Last enriched: 06/28/2026, 21:49:02 UTC
Last updated: 09/18/2026, 10:01:32 UTC
Views: 103
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