1. A method performed by a server comprising one or more computers, the method comprising: executing an application tier of an enterprise software application for receiving a plurality of Application Programming Interface (API) calls from a user device presenting a graphical user interface (GUI) for a presentation tier of the enterprise software application in a web browser, and for responding to the API calls; and executing an application tier security controller for checking the API calls against a mapping that maps each API call into a respective group with a respective user interface (UI) element of the GUI and a respective security key, and for authorizing user access to the application tier based on checking the API calls against the mapping.