Greyhat hackers have published the partial phone numbers belonging to more than 4.5 million Snapchat users after exploiting a recently disclosed security weakness that officials of the service had described as theoretical.
The database containing usernames and corresponding phone numbers for the majority of Snapchat users was posted to snapchatdb.info on the last day of 2013. Phone numbers published on the site were obscured by censoring the last two digits, but the anonymous people behind the posting said they might make the full version available privately.
Within 24 hours, the site was no longer accessible, but much of the data can still be found in search engine caches and mirror servers.
The data has also been incorporated into Have I Been Pwned, a whitehat service that helps people track whether their personal information has been leaked online.
The Snapchat data has likely also been downloaded by less scrupulous hackers for use in phishing and social engineering scams.