A new report from Yahoo! has said that all of its three billion user accounts were affected in a hacking attack dating back since 2013.
That's three billion accounts -- including emails, Tumblr, Fantasy and Flickr -- or three times more than the company initially reported in 2016.
The company, which was taken over by Verizon earlier this year, has said that an investigation show that the 2013 breach went much further than they originally thought.
Previously, the internet giant had said "more than one billion" of its accounts had been hit, however, the stolen data did not include passwords in clear text, payment card or bank account data, it added.
According to Yahoo, while its latest announcement did not represent a new "security issue", it was sending emails to all the "additional affected user accounts".
The company added that it was "continuing to work closely with law enforcement" to prevent further breaches from occuring.
A few months ago, Yahoo has been bought by US telecom firm, Verizon. The deal was completed on 13 June 2017.
The deal was first announced last year when the struggling company agreed to sell its main internet business to Verizon for a sum of $4.8bn.
That figure was later cut to $4.5bn after Yahoo! disclosed that it had been the victim, in 2013 and 2014, of two huge security breaches.
Verizon has combined its AOL subsidiary and Yahoo! into a new business called Oath.
Furthermore, in Tuesday's statement, Verizon's chief information security officer Chandra McMahon said: "Verizon is committed to the highest standards of accountability and transparency, and we proactively work to ensure the safety and security of our users and networks in an evolving landscape of online threats."
"Our investment in Yahoo is allowing that team to continue to take significant steps to enhance their security, as well as benefit from Verizon's experience and resources."
It's unclear who exactly was behind the 2013 break-in, but cybersecurity analysts reported in December that the stolen data was up for sale on the dark web, a murky network only accessible through certain software.
Whether or not people use Yahoo services, they should always practice proper computer hygiene, experts say, such as not reusing passwords and implementing two-factor authentication on all their accounts.
