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GHSA-5c4f-9pq9-6c77
winter/wn-cms-moduleImpact
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 backend user with any single Theme Editor permission (e.g. cms.manage_pages) to craft AJAX requests targeting template types outside their authorized scope — for example, deleting layouts, modifying partials, or reading content files.
In addition, the AssetList widget was registered for all users who passed the controller gate regardless of whether they held the cms.manage_assets permission, and its onUpload() handler was missing the validateRequestTheme() call that is present on all other mutating handlers in the same widget. This allowed unauthorized file uploads into the active theme's asset directory.
To actively exploit this security issue, an attacker would need access to the Backend with a user account with any of the following permissions:
cms.manage_pagescms.manage_partialscms.manage_layoutscms.manage_contentcms.manage_assets
The Winter CMS maintainers strongly recommend that all Winter CMS sites that rely on granular CMS permission assignments (specifically users with only access to cms.manage_content to only be able to edit content files through the Theme Editor) to update immediately.
Patches
Per-template-type permission checks are now enforced on all Theme Editor AJAX handlers, the AssetList widget is only registered for users with the cms.manage_assets permission, and onUpload() now includes theme validation consistent with the other mutating handlers.
This security issue has been fixed as of v1.2.13.
Workarounds
If users cannot upgrade, they may apply the following changes to their Winter CMS installation manually to resolve this issue:
- In
modules/cms/controllers/Index.php, wrap each widget registration in the constructor with the correspondinghasAccess()check, and add avalidateRequestType()call to theindex_onOpenTemplate(),onSave(),onCreateTemplate(),onDeleteTemplates(),onDelete(),onCommit(), andonReset()handlers that verifies the user holds the permission for the requested template type. - In
modules/cms/widgets/AssetList.php, add a$this->validateRequestTheme()call at the top of theonUpload()method.
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The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs high-level or administrative privileges. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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