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It's quite trivial to setup a method that implements "NSSelectorFromString" [1] etc.. and have it read from a Json payload send from a server. It's very hard for Apple to check for that unless they have active monitoring on apps after the review process.

[1] https://developer.apple.com/library/ios/documentation/Genera...

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Right. Any runtime behavior can be altered by observed state from outside the phone.

There's even a paper on intentionally inserting security flaws into your code and then exploiting them from your own server to change execution patterns:

https://www.usenix.org/conference/usenixsecurity13/technical...

Ultimately, you need to enforce access control instead of just trying to detect problems a priori. Apple's sandbox is a great start to that, and I expect they'll keep improving it to block apps like these.

The state doesn't even have to be from outside the phone. You could have an internal timer that kicks off 2 weeks after you've submitted to the App Store (to allow for unexpected delays) and switches on the evil behavior.

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