App Groups Are Not Secure by Default - Here's How to Fix That

If you're building an iOS app with a widget, a Watch companion (that's the watchOS app paired with your main iPhone app), or a Share Extension, you'll eventually need to pass data between processes. App Groups are the standard mechanism for this, and on the surface it looks simple: add the capability, write UserDefaults(suiteName:) , and off you go. But that apparent simplicity is exactly what causes problems. Data sits in an unencrypted container, any app from your team can read it, and incoming data validation is almost never done. Let's walk through how to set up App Groups properly, what actually belongs there, what risks exist, and how to organize a secure exchange - including a concrete example of passing an authorization token between an app and a widget. When You Can't Avoid App Groups iOS sandboxing is strict: every app lives in its own container, and by default there's no access to neighboring processes' files whatsoever. That's great for security, but it creates an obvious p