There have been two broad trends that have evolved since the first edition and will be covered in detail in this edition: Various new and modified technologies have appeared that are being used in web applications, including new remoting frameworks, HTML5, cross-domain integration techniques. Many new attack techniques have been developed, particularly in relation to the client side, including UI redress (clickjacking), framebusting, HTTP parameter pollution, XML external entity injection, bypasses for new browser anti-XSS filters, hybrid file (GIFAR) attacks. The web site to accompany the book will comprise: Code appearing in the book. Answers to the questions posed at the end of each chapter. Links to tools discussed in the book. A summarized methodology and checklist of tasks For several years the authors have delivered a very popular course on web application hacking at venues around the world, and they are constantly being asked to create an online version of the course for people who arent able to attend conferences. The authors will make parts of their existing course available online on a subscription basis in the coming months. They will use some examples from the online course within this second edition of the book, so that (in contrast to the first edition which uses purely fictional examples), people who wish to practice on the examples in the book will be able to do so if they wish. While there will be 25% new material and 25% revisions to existing materials, the reason for the amount of unmodified material is that a substantial part of the accumulated knowledge within web application security is timeless in character and has not materially altered for many years. This applies both to technology-agnostic design issues affecting areas like authentication and business logic, and also to many technology-specific areas such as code injection. In the latter case, developments in recent years have been relatively incremental, and consist of minor variations on existing techniques, or the application of existing techniques to updated technologies. The bulk of the first edition of WAHH could in fact have been written five years previously, and this classic material does not need updating. Rather, the focus for changes in the second edition will be on the areas of web application security where things have moved on in recent years, in relation to new technologies and attack techniques, primarily on the client-side.