The vulnerability stems from improper access control when querying via appId parameter to /container/list. In typical MVC architectures, this would involve: 1) A controller method handling the HTTP request parameters directly 2) A service layer method processing the business logic. The high confidence in ContainerController.listContainers comes from the direct mapping to the vulnerable endpoint and parameter. The service method is included with medium confidence as the actual data access would occur there, but without code we can't confirm implementation details. The core issue is missing authorization checks to verify the requesting user has rights to access containers associated with the specified appId.