Automated Discovery of Parameter Pollution Vulnerabilities in Web Applications.

In the last twenty years, web applications have grown from simple, static pages to complex, full-fledged dynamic applications. Typically, these applications are built using heterogeneous technologies and consist of code that runs both on the client and on the server. Even simple web applications today may accept and process hundreds of different HTTP parameters to be able to provide users with interactive services. While injection vulnerabilities such as SQL injection and cross-site scripting are well-known and have been intensively studied by the research community, a new class of injection vulnerabilities called HTTP Parameter Pollution (HPP) has not received as much attention. If a web application does not properly sanitize the user input for parameter delimiters, exploiting an HPP vulnerability, an attacker can compromise the logic of the application to perform either client-side or server-side attacks. In this paper, we present the first automated approach for the discovery of HTTP Parameter Pollution vulnerabilities in web applications. Using our prototype implementation called PAPAS (PArameter Pollution Analysis System), we conducted a large-scale analysis of more than 5,000 popular websites. Our experimental results show that about 30% of the websites that we analyzed contain vulnerable parameters and that 46.8% of the vulnerabilities we discovered (i.e., 14% of the total websites) can be exploited via HPP attacks. The fact that PAPAS was able to find vulnerabilities in many high-profile, well-known websites suggests that many developers are not aware of the HPP problem. We informed a number of major websites about the vulnerabilities we identified, and our findings were confirmed.