Information flow analysis for javascript

Modern Web 2.0 pages combine scripts from several sources into a single client-side JavaScript program with almost no isolation. In order to prevent attacks from an untrusted third-party script or cross-site scripting, tracking provenance of data is imperative. However, no browser offers this security mechanism. This work presents the first information flow control mechanism for full JavaScript. We track information flow dynamically as much as possible but rely on intra-procedural static analysis to capture implicit flow. Our analysis handles even the dreaded eval function soundly and incorporates flow based on JavaScript's prototype inheritance. We implemented our analysis in a production JavaScript engine and report both qualitative as well as quantitative evaluation results.