Every single Yahoo account was affected in a 2013 data breach, bringing the total from 1 billion to 3 billion.
Article Link: https://www.darkreading.com/attacks-breaches/yahoo-all-3-billion-accounts-affected-in-2013-breach/d/d-id/1330039?_mc=rss_x_drr_edt_aud_dr_x_x-rss-simple