Sign in
Deutsch English Español Polski
Medium

Concrete CMS has a stored Cross-site Scripting (XSS) vulnerability

  • Disclosed: 04.03.2026
  • Updated: 11.10.2026 10:22

In Concrete CMS below version 9.4.8, a Cross-site Scripting (XSS) vulnerability exists in the "Legacy Form" block. An authenticated user with permissions to create or edit forms (e.g., a rogue administrator) can inject a persistent JavaScript payload into the options of a multiple-choice question (Checkbox List, Radio Buttons, or Select Box). This payload is then executed in the browser of any user who views the page containing the form. 

The Concrete CMS security team thanks M3dium for reporting.

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
Composer package concrete5/concrete5 < 9.4.8 9.4.8

References

CVSS score 4.8/10
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
Weakness (CWE)
CWE-79
Platform
Composer
Package
concrete5/concrete5
Disclosed
04.03.2026
Updated
11.10.2026 10:22

Sources and licenses

OSV / GitHub Advisory Database - GHSA-f4vq-pj32-gr4q - CC BY 4.0

Vulnerability history: concrete5/concrete5

All published vulnerabilities of this package (Composer package), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (121) in the archive
Total entries
121
First → latest
10.2021 06.2026
Without a fix
10
Exploited in attacks
0

Severity breakdown

  • Critical 2
  • High 16
  • Medium 65
  • Low 38

Disclosures per year

Severity:
  1. Concrete CMS: PHP Object Injection via unserialize() calls
    High CVE-2026-10721 < 9.5.2 9.5.2
  2. Concrete CMS is vulnerable to PHP Object Injection via unserialize() calls in the Workflow, Form block, and File/Set components
    High CVE-2026-7888 < 9.5.2 9.5.2
  3. Concrete does not validate a CSRF token before processing requests to `/dashboard/extend/update/do_update/<pkgHandle>`
    High CVE-2026-8417 < 9.5.1 9.5.1
  4. Concrete CMS does not validate a CSRF token before processing requests to `/dashboard/extend/update/prepare_remote_upgrade/<remoteMPID>`
    High CVE-2026-8426 < 9.5.1 9.5.1
  5. Concrete CMS contains a CSRF vulnerability
    High CVE-2026-8421 < 9.5.1 9.5.1
  6. Concrete CMS is Vulnerable to Cross-Site Request Forgery
    High CVE-2026-8428 < 9.5.1 9.5.1
  7. Concrete CMS is vulnerable to missing authorization in the bulk_user_assignment.php
    High CVE-2026-8350 < 9.5.1 9.5.1
  8. Concrete CMS has Stored XSS through its height parameter
    High CVE-2026-8203 < 9.5.1 9.5.1
  9. Concrete CMS is Vulnerable to Cross-Site Request Forgery
    High CVE-2026-8140 < 9.5.1 9.5.1
  10. Concrete CMS Vulnerable to Deserialization of Untrusted Data
    High CVE-2026-8135 < 9.5.1 9.5.1
  11. Concrete CMS is vulnerable to Stored XSS via OAuth integration name
    High CVE-2026-8197 < 9.5.1 9.5.1
  12. Concrete CMS Vulnerable to Relative Path Traversal
    Critical · 7.2 CVE-2026-8134 < 9.5.1 9.5.1
  13. Concrete CMS has a stored Cross-site Scripting (XSS) vulnerability this entry
    Medium · 4.8 CVE-2026-3241 < 9.4.8 9.4.8
  14. Concrete CMS vulnerable to Remote Code Execution by stored PHP object injection
    High CVE-2026-3452 < 9.4.8 9.4.8
  15. Concrete CMS (previously concrete5) is vulnerable to possible auth bypass in the jobs section
    Critical · 9.8 CVE-2023-28473 < 9.2.0 9.2.0
  16. Concrete CMS vulnerable to Cross-site Request Forgery
    High · 8.8 CVE-2022-43693 < 8.5.10, >= 9.0.0RC1, < 9.1.3 8.5.10, 9.1.3
  17. Cross Site Request Forgery in concrete5/concrete5
    High CVE-2021-22954 < 9.0.0 9.0.0
  18. Unrestricted Uploads in Concrete5
    High · 7.2 CVE-2020-11476 < 8.5.3 8.5.3
  19. Server-Side Request Forgery vulnerability in concrete5
    High · 8.2 CVE-2021-22958 < 8.5.5 8.5.5

Know which vulnerabilities affect your application

With the DockRay integration and software inventory enabled, DockRay checks reported component versions against known vulnerabilities and notifies you about confirmed matches. Coverage depends on the supported technology and available advisory data.

Connect your application
DockRay newsletter

Application security in your inbox

Important vulnerabilities, actionable guidance and practical advice for your applications. Choose your technologies and follow what matters to your project.

  • A daily digest of new vulnerabilities, critical ones included.
  • Notifications about important updates.
  • Practical advice on application security and monitoring.

Leave empty to receive updates for every technology.

Privacy policy

Free to subscribe. Unsubscribe with one click in any email.