Winter is a free, open-source content management system (CMS) based on the Laravel PHP framework. Prior to 1.2.13, custom CSS supplied through the Brand Settings Styles field by a backend user with the backend.manage_branding permission is compiled by the LESS parser and rendered without sanitization on every backend page, allowing stored cross-site scripting against backend users. This issue is fixed in version 1.2.13.

CVE-2026-32257 affects Winter CMS, an open-source CMS built on the Laravel PHP framework. Prior to version 1.2.13, a backend user with the backend.manage_branding permission could inject malicious custom CSS through the Brand Settings Styles field. This CSS is processed by the LESS parser and rendered without sanitization on every backend page, enabling a stored cross-site scripting (XSS) attack against other backend users. The vulnerability requires an authenticated user with specific branding permissions to exploit, limiting its attack surface but still posing a significant risk in multi-user environments. The issue has been patched in Winter CMS version 1.2.13. A fix commit and a GitHub Security Advisory have been published alongside the CVE disclosure.