The present invention relates to a solution to improve the security of applications. Particularly, the invention relates to the control of the whole lifecycle of data traffic between a client and a server applying also internal data flow system within the server only for editable data. The invention presents a method for detection of manipulation of data (29) by a client (11, 15, 25) that performs a request to a server (13, 17, 27) and detection of vulnerabilities within source code. The invention also presents an application and a system for the detection of manipulation in applications. As a particular example, the invention presents a method for detection of manipulation of web pages in HTTP.