title: Prevent iOS URL scheme hijack
body: <p>I have an app that gets opened from another app via a URL scheme. The URL contains signup tokens. As any app can register the same URL scheme as my app, I am concerned a "fake" app can do a man-in-the-middle attack and capture the signup tokens.</p>
  
  <p>My idea is to check that the URL scheme does not open another app when my app is first opened.</p>
  
  <p>From a security perspective, if the URL scheme opens my app the first time, will it always open my app in the future?</p>