Vulnerability Instance

October CMS has Safe Mode Bypass via CSS Preprocessor Compilers
A server-side information disclosure vulnerability was identified in the handling of CSS preprocessor files. Backend users with Editor permissions could craft `.less`, `.sass`, or `.scss` files that leverage the compiler's import functionality to read arbitrary files from the server. This worked even with `cms.safe_mode` enabled.

### Impact
- Potential exposure of sensitive server-side files
- Requires authenticated backend access with Editor permissions
- Only relevant when `cms.safe_mode` is enabled (otherwise direct PHP injection is already possible)

### Patches
The vulnerability has been patched in v3.7.14 and v4.1.10. When `cms.safe_mode` is enabled, `.less`, `.sass`, and `.scss` files can no longer be created, uploaded, or edited across the CMS editor, media manager, and file upload interfaces. All users are encouraged to upgrade to the latest patched version.

### Workarounds
If upgrading immediately is not possible:
- Set `cms.editable_asset_types` config to `['css', 'js']` to remove preprocessor file types from the editor
- Restrict Editor tool access to fully trusted administrators only

- Reported by [Chris Alupului](https://github.com/neosprings)