Phone numbers linked to more than 400 million Facebook accounts were listed online in the latest privacy lapse for the social media giant, US media are reporting.
An exposed server stored 419 million records on users across several databases - including 133 million US accounts, more than 50 million in Vietnam, and 18 million in Britain, according to technology news site TechCruch.
The databases listed Facebook user IDs - unique digits attached to each account - the profiles' phone numbers, as well as the gender listed by some accounts and their geographical locations, technology website TechCrunch reported.
The server was not password protected, meaning anyone could access the databases, and remained online until late Wednesday when TechCrunch contacted the site's host.
Facebook confirmed parts of the report but downplayed the extent of the exposure, saying that the number of accounts so far confirmed was around half of the reported 419 million.
It added that many of the entries were duplicates and that the data was old.
"The dataset has been taken down and we have seen no evidence that Facebook accounts were compromised," a Facebook spokesperson told AFP.
Following the 2018 Cambridge Analytica scandal, when a firm used Facebook's lax privacy settings to access millions of users' personal details, the company disabled a feature that allowed users to search the platform by phone numbers.
The exposure of a user's phone number leaves them vulnerable to spam calls, SIM-swapping - as recently happened to Twitter CEO Jack Dorsey - with hackers able to force-reset the passwords of the compromised accounts.
What about users in Malta?
Contacted, a spokesman from Malta's Office of the Information and Data Protection Commissioner said the Irish Data Protection Commission, as the lead supervisory data protection authority for Facebook in Europe, has contacted the social media giant on this case and are "waiting for their answers".
"This was confirmed by a spokesman for the Irish DPC yesterday in comments given to POLITICO. At this very early stage since when this leak was unearthed, this is the only information that we are in a position to provide," the spokesman told Times of Malta.