CVE-2026-55790 Craft CMS: DOM XSS via GitHub issue title in CraftSupport widget
An attacker can execute arbitrary JavaScript in a Craft CMS admin's session by poisoning a GitHub issue title viewed in the support widget.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-55790?
CVE-2026-55790 is a high-severity cross-site scripting vulnerability in craftcms cms, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Craft CMS is a content management system (CMS). In versions 5.0.0-RC1 through 5.9.22 and 4.0.0-RC1 through 4.17.15, an attacker with only a GitHub account can plant a JavaScript payload in a craftcms/cms issue title. When a Craft admin uses the CraftSupport widget’s "Give feedback" screen and types a search term that returns the poisoned issue, the payload executes in the admin’s control panel session. No control panel account or elevated privileges are required on the attacker’s side. This issue has been fixed in versions 4.17.16 and 5.9.23.
Weakness: CWE-79
Which versions are affected by CVE-2026-55790?
4 open source packages ship an affected version, including craftcms/cms.
| Package | Affected | Fixed in |
|---|---|---|
craftcms/cms Packagist | From 4.0.0-RC1 | 4.17.16 |
craftcms/cms Packagist | From 4.0.0-RC1 | 4.17.16 |
craftcms/cms Packagist | From 5.0.0-RC1 | 5.9.23 |
craftcms/cms Packagist | From 5.0.0-RC1 | 5.9.23 |
How do I fix CVE-2026-55790?
Upgrade craftcms/cms to a fixed version for your release line: 4.17.16 or 5.9.23.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-55790 being exploited?
There is no known exploitation of CVE-2026-55790 in the wild and no public exploit code.
Sources
Also known as GHSA-24x4-j6x9-rfw5.