title: Attack Protection for iOS In-App Purchases
body: <p>Apple's iOS in-app purchase system has been attacked in the past by people who have tricked apps into giving them content for free.  They have since improved the systems involved to try to limit this kind of thing.</p>
  
  <p>I've read through the StoreKit reference documents available from Apple and I have a general idea of the workflow and the checks that need to be done, and so on.  However, there may be security issues that I'm not aware of.</p>
  
  <p>Can anyone provide a full list of theft-attacks that can be attempted against In-App purchase mechanisms, how developers might mistakenly allow these attacks, and what are best practices for preventing them?</p>