Summaryinfo

A vulnerability, which was classified as problematic, has been found in Craft CMS. Affected by this issue is the function setReturnUrl of the component Return URL Handler. The manipulation leads to cross site scripting. This vulnerability is documented as CVE-2026-31859. The attack can be initiated remotely. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Craft CMS (affected version unknown). It has been rated as problematic. This issue affects the function setReturnUrl of the component Return URL Handler. The manipulation with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Impacted is integrity. The summary by CVE is:

Craft is a content management system (CMS). The fix for CVE-2025-35939 in craftcms/cms introduced a strip_tags() call in src/web/User.php to sanitize return URLs before they are stored in the session. However, strip_tags() only removes HTML tags (angle brackets) -- it does not inspect or filter URL schemes. Payloads like javascript:alert(document.cookie) contain no HTML tags and pass through strip_tags() completely unmodified, enabling reflected XSS when the return URL is rendered in an href attribute. This vulnerability is fixed in 5.9.7 and 4.17.3.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-31859. The exploitation is known to be easy. The attack may be initiated remotely. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

Upgrading eliminates this vulnerability.

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Productinfo

Type

• Content Management System

Vendor

• Craft

Name

• CMS

License

• free

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CPE 2.2info

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