Apple has now banned cryptocurrency mining from its iOS devices. Developers will no longer be able to release apps that features the mining.
Some developers previously sneaked cryptocurrency mining into their apps, Apple has now changed their app store rules to stop this. You can see the change to the rule below.
Design your app to use power efficiently. Apps should not rapidly drain battery, generate excessive heat, or put unnecessary strain on device resources. Apps, including any third party advertisements displayed within them, may not run unrelated background processes, such as cryptocurrency mining.
This happened previously with an app on the app store called Calendar 2 that was mini cryptocurrency in the background without its users knowing. It looks like the new rule will also stop any apps which have been developed to actually mine the currency.
Source Business Insider