Techniques for handling security of an application and its extension are described. In one embodiment, an application manager of an operating system running within a data processing system launches an application in a first sandboxed environment based on a first security profile associated with the application. In response to receiving a request from the application for accessing a function of an application extension that is associated with the application, the application manager launches the application extension in a second sandboxed environment based on a second security profile associated with the application extension. The application manager is to individually enforce security and manage resources of the application and the application extension in the first and second sandboxed environments based on the first and second security profiles, respectively. The second security profile specifies resources fewer than the first security profile.