Emails that have been published as part of the Epic Games v. Apple trial have revealed that back in 2015, 128 million iOS users installed 2,500+ infected apps that were affected by the XcodeGhost malware. The malware was placed inside apps that appeared to be legitimate and at the time it was believed to be the largest hack against iPhone users based on the number of people affected. Of the aforementioned 128 million users impacted, 18 million were from the U.S.
128 million iOS users installed 2500+ malware infected apps in 2015 including popular titles like WeChat and Angry Birds 2
The malware was used to mine data from iOS users and Dale Bagwell, Apple's manager of iTunes customer experience, said that there were 203 million downloads of the those 2500+ malware-laden apps. Another Apple employee wrote in an email that "China represents 55% of customers and 66% of downloads. As you can see, a significant number (18 million customers) are affected in the US."