View article

Despite the considerable amounts of resources invested into securing the Web, Cross-Site Scripting (XSS) is still widespread. This is especially true for Client-Side XSS as, unlike server-side application frameworks, Web browsers do not ship with standard protection routines, so-called sanitizers. Web developers, therefore, have to either resort to third-party libraries or write their own sanitizers to stop XSS in its tracks. Such custom sanitizer routines – dubbed hand sanitizers in the following – are notoriously difficult to implement securely. In this paper, we present a technique to automatically detect, extract, analyze, and validate JavaScript sanitizer functions using a combination of taint tracking and symbolic string analysis. While existing work evaluates server-side sanitizers using a small number of applications, we present the first large-scale study of client-side JavaScript sanitizers. Of the most popular 20,000 …