Ratproxy: A Web Application Security Audit Tool

"A semi-automated, largely passive web application security audit tool, optimized for an accurate and sensitive detection, and automatic annotation, of potential problems and security-relevant design patterns based on the observation of existing, user-initiated traffic in complex web 2.0 environments. Detects and prioritizes broad classes of security problems, such as dynamic cross-site trust model considerations, script inclusion issues, content serving problems, insufficient XSRF and XSS defenses, and much more." read more...

Website: http://code.google.com/p/ratproxy