https://www.theverge.com/2017/10/3/16414306/yahoo-security-data-breach-3-billion-verizon

Yahoo today announced that the huge data breach in August 2013 affected every user on its service — that’s all three billion users and up from the initial one billion number Yahoo initially reported. Since disclosing the hack, Yahoo continued to add more numbers of accounts compromised, but today’s announcement makes it clear that if you had a Yahoo email account, you were part of the breach.