In the provided code snippet:
```php
$design_file_path = APP_ROOT . '/templates/themes/' . $design . '.php';
```
The `design` variable is concatenated to create a file path, which could pose a security risk if `$design` is not properly validated or sanitized. An attacker might exploit this by crafting a value for `$design` that points to a file outside of the intended directory.
For instance, if there are no checks in place, an attacker might


