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. Under the mandated rules. The section also bans apps and any third-party ads from running "unrelated background processes, such as cryptocurrency mining".
The guidelines reference cryptocurrency mining in two places, in a section about power efficiency (2.4.2) and a separate Cryptocurrencies section (3.1.5).
This isn't the first time that the iPhone maker has taken action against mining apps. These conditions extend to apps providing cryptocurrency futures trading, and other crypto-securities or quasi-securities trading.
Addressing the rising frauds with the unregulated initial coin offering-based (ICO) fundraising technique, Apple is now only allowing apps from established banks, securities firms, futures commission merchants ("FCM"), or other approved financial institutions.
ICOs must comply with "all applicable laws", Apple said.
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 updated its App Store review guidelines last week, during the WWDC 2018 conference.
In July 2017, Apple 'approved' Dash as a cryptocurrency. "Apps may facilitate virtual currency storage, provided they are offered by developers enrolled as an organization", the policy states. On macOS, however, users will continue to be able to acquire apps outside of the Mac App Store, enabling mining and other activities to continue without Apple's seal of approval. Exchanges can offer fully-featured apps offering trading abilities, as long as the apps are issued by the exchanges themselves and not third parties.
Finally, the world's most valuable company has also mandated that apps do not offer cryptocurrency as rewards to users for completing tasks.