Craft CMS 4.x before 4.18.8 and 5.x before 5.11.0 contains a remote code execution vulnerability in the Twig group filter, which invokes non-string arrow arguments as callables without the checkArrow guard used by other arrow-accepting filters. Authenticated control panel users can pass an array-callable such as FileHelper::writeToFile via element-select condition rules to write a webshell to the webroot and execute code as the web user.
https://github.com/craftcms/cms/security/advisories/GHSA-xmwr-88vw-5ghh
Published: 2026-10-19
Updated: 2026-10-19
Base Score: 9
Vector: CVSS2#AV:N/AC:L/Au:S/C:C/I:C/A:C
Severity: High
Base Score: 8.8
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Severity: High
Base Score: 8.7
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Severity: High