Yahoo suffers world’s biggest hack affecting 1 billion users

Yahoo has discovered a 3-year-old security breach that enabled a hacker to compromise more than 1 billion user accounts.

The digital heist disclosed Wednesday occurred in August 2013, more than a year before a separate hack that Yahoo announced nearly three months ago. That breach affected at least 500 million users, which had been the most far-reaching hack until the latest revelation.

“It’s shocking,” security expert Avivah Litan of Gartner Inc.

Both lapses occurred during the reign of Yahoo CEO Marissa Mayer, a once-lauded leader who found herself unable to turn around the company in the four years since her arrival. Earlier this year, Yahoo agreed to sell its digital operations to Verizon Communications for $4.8 billion a deal that may now be imperiled by the hacking revelations.