The latest update to the iPhone’s operating system features a new privacy feature called App Tracking Transparency. WSJ’s Joanna Stern spoke exclusively with Apple’s Craig Federighi about the decisions behind the feature, as well as Apple's interest in mixed reality—and the possibility he'll replace Tim Cook as CEO. Photo illustration: Alex Kuzoian for The Wall Street Journal More from the Wall Street Journal: Visit WSJ.com: http://www.wsj.com/ Visit the WSJ Video Center: https://wsj.com/video On Facebook: https://www.facebook.com/pg/wsj/videos/ On Twitter: https://twitter.com/WSJ On Snapchat: https://on.wsj.com/2ratjSM #WSJ #Apple #iOS14