From Wired:

In the months since, Wardle has worked on and off to deconstruct that emoji mystery. What he found—and helped Apple fix—wasn’t the targeted hacking of his friend’s iPhone. Instead, it was an unintentional bug in a very intentional censorship feature, one that Apple includes in every iPhone in the world in an apparent attempt to placate the Chinese government. “Basically, Apple added some code to iOS with the goal that phones in China wouldn’t display a Taiwanese flag,” Wardle says, “and there was a bug in that code.”