Advisories for Composer/Winter/Wn-Cms-Module package

2026

Winter: Broken access control in `Cms\Controllers\Index` allows cross-template actions and unauthorized asset uploads

Affected versions of Winter CMS did not enforce per-template-type permission checks in the CMS section's AJAX handlers. The CMS controller (Cms\Controllers\Index) used OR-logic across its five permissions (cms.manage_pages, cms.manage_partials, cms.manage_layouts, cms.manage_content, cms.manage_assets) to control access to the section as a whole, but individual handlers such as onSave(), onDelete(), and onDeleteTemplates() did not verify that the authenticated user holds the specific permission corresponding to the requested template type. This allowed a …

Winter CMS has Stored Cross-site Scripting (XSS) in Asset Manager

Affected versions of Winter CMS allow users with access to the CMS Asset Manager were able to upload SVGs without automatic sanitization. To actively exploit this security issue, an attacker would need access to the Backend with a user account with the following permission: cms.manage_assets The Winter CMS maintainers strongly recommend that the cms.manage_assets permission only be reserved to trusted administrators and developers in general.

2024

Winter CMS Modules allows a sandbox bypass in Twig templates leading to data modification and deletion

Affected versions of Winter CMS allow users with access to the CMS templates sections that modify Twig files to bypass the sandbox placed on Twig files and modify resources such as theme customisation values or modify, or remove, templates in the theme even if not provided direct access via the permissions. As all objects passed through to Twig are references to the live objects, it is also possible to also …