If you had a Yahoo account in 2013, it's likely you were hacked. The company announced that an investigation into the breach showed "all Yahoo user accounts were affected."
When the company revealed the attack last year during its merger with Verizon, it estimated more than 1 billion accounts had been compromised. After an investigation by "outside forensic experts," it was determined that all of the roughly 3 billion accounts had been affected.
The good news: The investigation showed sensitive material like credit card data wasn't stolen.
Keep in mind, that breach is separate from a 2014 hack that compromised a half-billion accounts. That attack didn't include payment or banking information either.