How to find out what the app (Android/IOS) has been modified?

For example apps, put on resources like 4pda. In many cases, the modified application is clearly marked in the post, specified modified functionality. What if the person modified the application, but decided not to specify it and put it on the site as genuine? Are there any (if so which) means/methods of application verification change third parties? (Not versed in mobile development, just interested in the topic)
March 19th 20 at 09:25
3 answers
March 19th 20 at 09:27
unpack the package (zip it) and compare with the original papilova the same or close version

to find the original, you must install it on the phone (android) and using adb backup package to restore it apk.
March 19th 20 at 09:29
Download the same app from the official source, compare the checksum (or even bitwise) with suspicious.
So you can see what code exactly was removed/added/changed on the original or just the common true/not true? - gerry33 commented on March 19th 20 at 09:32
@gerry33, the second - Brenda28 commented on March 19th 20 at 09:35
March 19th 20 at 09:31
In iOS this is not true. In 99% of cases you will be downloading apps from the store and no where more.

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