Craft CMS has authenticated path traversal in `assets/icon`, allowing local `.svg` file read

### Summary An authenticated path traversal in `assets/icon` allows local SVG file read by passing traversal sequences in the `extension` parameter. The issue is caused by file existence checks happening before extension validation. ### Details The endpoint: - `src/controllers/AssetsController.php:1115-1123` - `actionIcon(string $extension)` calls `Assets::iconPath($extension)` and returns `sendFile($path, ...)`. In `Assets::iconPath()`: - Path is built from user-controlled `extension`: - `src/helpers/Assets.php:906-909` - If `file_exists($path)` is true, path is returned immediately: - `src/helpers/Assets.php:910-912` Validation exists in `Assets::iconSvg()`: - `preg_match('/^\w+$/', $extension)` - `src/helpers/Assets.php:927-931` However, that validation is only reached if `iconPath()` does **not** find a file. So traversal payloads that resolve to existing `.svg` files bypass validation and are served by `sendFile()`. ### Impact - Authenticated users can read local .svg files accessible to the application process. ### References - https://github.com/craftcms/cms/commit/30f5f1a8d6edf0f3a00be72c42c78d9dc7d72d5c