According to a former Yahoo executive the number of affected user accounts in the Yahoo data breach may be between 1 Billion and 3 Billion. This summer 200 million Yahoo user accounts were offered for sale in a black market on the dark web. The experts from the intelligence firm InfoArmor that investigated the incident claim the data breach is the result of a cyber attack conducted by cyber criminals that later sold the user accounts to an Eastern European nation-state actor. The sad aspect of the story is that Yahoo could have protected its users with a password reset.”]
Source: https://securityaffairs.co/wordpress/51833/data-breach/yahoo-data-breach-2.html