HTTP Parameter Pollution (HPP) - SEaCURE.it presentation by Luca Carettoni and Stefano Di Paola
Throughout this presentation, we will present a new attack technique called HTTP Parameter Pollution (HPP). We will examine with a fresh perspective a newly discovered input validation flaw, while demonstrating new threats and possible attack scenarios. Such injection can be defined as the possibility to override the HTTP GET/POST parameters within the query string. In such situations, an attacker may replace existent values which are normally hardcoded and not accessible. In many cases it can be used to modify the behaviors of client-side and server-side applications, to exploit vulnerabilities in uncontrollable variables as well as bypassing web application firewalls. Some of the attacks covered in this talk have been discovered in real-world applications.
Although input validation vulnerabilities are a well-known subject in the web application security field and are extensively covered by several researchers, it is quite surprising that no formal definition of the HPP attack was previously published, as far as we know. Once again, it is a clear demonstration of how important is to develop comprehensive input validation filters in order to manage new incoming web application threats