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The Web Application Hacker's Handbook: Finding and Exploiting Security Flaws, 2nd Edition by Marcus Pinto, Dafydd Stuttard

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Summary

Despite their extensive differences, virtually all web applications employ the same core security mechanisms in some shape or form. These mechanisms represent an application's primary defenses against malicious users and therefore also comprise the bulk of the application's attack surface. The vulnerabilities we will examine later in this book mainly arise from defects within these core mechanisms.

Of these components, the mechanisms for handling user access and user input are the most important and should receive most of your attention when you are targeting an application. Defects in these mechanisms often lead to complete compromise of the application, enabling you to access data belonging to other users, perform unauthorized actions, and inject arbitrary code and commands.

Questions

Answers can be found at http://mdsec.net/wahh.

  1. Why are an application's mechanisms for handling user access only as strong as the weakest of these components?
  2. What is the difference between a session and a session token?
  3. Why is it not always possible to use a whitelist-based approach to input validation?
  4. You are attacking an application that implements an administrative function. You do not have any valid credentials to use the function. Why should you nevertheless pay close attention to it?
  5. An input validation mechanism designed to block cross-site scripting attacks performs the following sequence of steps on an item of input:
    1. Strip any <script> expressions that appear.
    2. Truncate the input ...

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