S2XS2: A Server Side Approach to Automatically Detect XSS Attacks

Cross site scripting (XSS) vulnerabilities are widespread in web-based programs. Server side detection of suspected contents can mitigate XSS exploitations early. Unfortunately, existing serve side approaches impose modification of server and client side environments. In this paper, we develop an automated framework to detect XSS attacks at the server side based on the notion of boundary injection and policy generation. Boundaries mark content generation locations in server script code. We derive expected benign features of dynamic contents that are matched during response page generation to detect attacks. We develop a prototype tool to automatically insert boundaries and generate policies for JSP programs. We evaluate the approach with four JSP programs. The results indicate that the approach detects most of the well known XSS attacks. Moreover, the false positive rates vary between zero and 5.2%. The approach suffers from negligible runtime overhead.