https://motherboard.vice.com/en_us/article/8x8b4x/whoops-yahoo-says-2013-hack-actually-hit-3-billion-users

Remember the Yahoo hack? Yes, that's a tough question, because there were at least two separate massive Yahoo hacks revealed in 2016. The first one, which occurred in 2013, hit 500 million users, a number that then climbed to 1 billion. The second, which occurred in late 2014, hit 500 million users globally.

The company revealed on Tuesday that the 2013 breach actually hit 3 billion users—virtually every single individual who ever had a Yahoo email account. Oath, the new name Yahoo got after Verizon bought it last year, disclosed the figure in a new filing.