A popular calendar app for Mac has gone missing from Apple’s App Store after it was revealed that it was mining cryptocurrency without the user’s consent.

The app, Calendar 2, was open about using Mac’s CPU for mining cryptocurrency (Monero), this being devised to act as an alternative payment method which would unlock premium features.

This meant that Calendar 2 had a free version and a version that came with advanced feature which could have been unlocked through one-off or subscription payment – but if you didn’t prefer any of the aforementioned payment methods, you had the option of unlocking the additional features by giving the app permission to use your processor for crypto mining.

Mining Without Consent

The issue was that even if the user selected the free version of the app, and hadn’t given its permission, the software would still mine cryptocurrency. This was due to a bug in the app’s code, explained the developer (Qbix).

Qbix founder Gregory Magarshak, also disclosed that there was a second bug which caused the mining operations to use more CPU cycles than the 10-20% of processor usage that was initially calculated, reports Apple Insider.

In light of these findings, Magarshak stated that he would remove the mining feature from the app, but Calendar 2 was then taken down from the Mac App Store (still currently being unavailable).

It’s not yet known if the developer took down the app or Apple removed the software. What also remains unclear is Apple’s take on this potential new payment option for unlocking premium features.

This incident point out the possible risks of running such a cryptocurrency mining script to unlock an app’s advanced features, especially when there is the possibility of mining without the user’s permission or knowledge.

It remains to be see what the developers will do with Calendar 2, or if Apple will disapprove of this kind of mining scheme to be used as a payment option for certain features.