https://qz.com/1094288/yahoo-data-breach-what-should-i-do-about-my-yahoo-account/

If you’re still reeling over the Equifax hack, consider this: its 145.5 million potential victims look like chump change compared to what’s happening with Yahoo users. Parent company Verizon announced yesterday (Oct. 3) that “following an investigation with the assistance of outside forensic experts” a 2013 hack estimated to have affected 1 billion user accounts actually affected every single account that existed at the time—a staggering 3 billion.

Names, email addresses, hashed passwords, birthdays, phone numbers, and, in some cases, security questions and answers could have all been compromised.