Yahoo on Tuesday said that every single Yahoo account was affected by a data breach that took place in 2013.
In 2016, Yahoo disclosed that more than one billion of about three billion accounts had likely been affected by the hack. In its disclosure Tuesday, the company said all accounts were likely victimized.
Yahoo included the finding in a recent update to its Account Security Update page, saying that it found out about the wider breach through new intelligence obtained during the company's integration into Verizon Communications (NYSE: VZ). Outside forensic experts assisted in the discovery.
Yahoo said it will begin alerting accounts that weren't previously notified of the attack.
Four years ago, a breach allowed attackers to steal email addresses, passwords, birth dates, telephone numbers and more. The more recent probe indicated that stolen information didn't include passwords in clear text, payment card data or information about bank accounts.
Verizon finished its acquisition of Yahoo in June and is folding it, with AOL, under a new subsidiary named Oath.
The Oath portfolio includes HuffPost, Yahoo Sports, AOL.com, MAKERS, Tumblr, BUILD Studios, Yahoo Finance, Yahoo Mail and more, with a mission to build brands people love.
Verizon, headquartered in New York City, employs 161,000 people and generated nearly $126 billion in 2016 revenues.
Verizon shares dipped two cents to $49.83 midday Wednesday, within a 52-week trading range of $42.80 to $54.83.
