If you have evaluated AJAX (Asynchronous JavaScript and XML) for your next Web application development project, then you probably have read or heard a great deal about AJAX security concerns and the claim that AJAX increases the attack surface for hackers. If you are a skilled security developer, you might wonder whether the AJAX security problem originates in the technologies involved or whether lack of security in AJAX is a misconception. Security threats like SQL injection, cross-site scripting (XSS), message spoofing, and failed input validation existed before in Web applications and have been solved many times since then.