https://techcrunch.com/2017/10/03/yahoo-says-all-3b-accounts-were-impacted-by-2013-breach-not-1b-as-thought/

Internet giant Yahoo’s 2013 security breach has dealt the company yet another blow. Today Yahoo sent out a notice disclosing that a further investigation of the “cookie forging” breach has produced new evidence. The company now believes that all of its three billion accounts were impacted, not 1 billion as it previously thought. This will include all people who have Yahoo emails, and all people who had registered for any other Yahoo service like Flickr or fantasy sports.

The company, now a part of Oath after it was acquired by Verizon for $4.5 billion and merged with AOL (which also owns TechCrunch), tried to mitigate the blow today by noting that when the 2013 breach was discovered and disclosed — in 2016 — the company “took action to protect all accounts.”