In an update to the Hardware Compatibility section of its developer guidelines, Apple said "apps, including any third party advertisements displayed with them, may not run unrelated background processes, such as cryptocurrency mining".
The promising thing here is that Apple seem very open to the idea of new apps being produced which will integrate the use of cryptocurrencies. News about Apple's changes to the App Store aren't likely to play particularly well.
Apple has put restrictions on apps that mine cryptocurrencies using device processing power, specifically disallowing such programs in its App Store.
(Kitco News) - Tech giant Apple has taken a major step against cryptocurrencies by outlawing digital mining on all of its devices, including iPhones, iPads, iMacs, MacBook Pros, and others. "Apps may not mine for cryptocurrencies unless the processing is performed off device (e.g. cloud-based mining)", Apple's new App Store guidelines say. These conditions extend to apps providing cryptocurrency futures trading, and other crypto-securities or quasi-securities trading.
Apple Bans Cryptocurrency Mining Apps on iOS Devices
Such extensions will still work with Safari 12, but being depreciated means it's only a matter of time until support is dropped entirely, at which point only Safari App Extensions will work.
Apple has been pushing extension developers toward Safari App Extensions for a few years now.
This is the first time Apple has offered a clear stance on its policy on cryptocurrency apps. The app even made it to number 3 in the finance category of the App Store before Apple pulled it down.
Similarly, Apple is also allowing apps to facilitate crypto transactions "on an approved exchange, provided they are offered by the exchange itself". In a dedicated cryptocurrency section, the company goes on to break down in more detail what is - and, crucially, is not - permissible. Finally, cryptocurrency apps can't offer currency as a reward for downloading other apps, posting to social networks or encouraging other users to download apps.