"We have contacted browser makers to ensure that known malicious extensions are no longer available to download in their stores and to share information that could help identify additional extensions that may be related", Rosen said. Facebook has claimed that the data theft wasn't the company's fault.
The data trove has surfaced shortly after Facebook confirmed that 29 million users had their accounts accessed by hackers.
What's going on: Hackers told BBC News they have access to 120 million accounts, which they are attempting to sell to interested parties.
The other key difference between the two hacks are the targets: the personal information that was stolen seemed primarily to focus on American accounts while the more recent browser hack targeted users living in Ukraine and Russian Federation.
Data from a further 176,000 accounts was also made available, although some of the information - including email addresses and phone numbers - could have been scraped from members who had not hidden it.
The BBC Russian service contacted the five Russian users whose messages were uploaded by FBSaler and the post were theirs.
Facebook is under the microscope ever since the Cambridge Analytica scandal came to light and the social networking platform is trying to deal with every situation carefully. Rosen said the social network had notified law enforcement, had the website hosting the Facebook account data had been taken down.
"One example included photographs of a recent holiday, another was a chat about a recent Depeche Mode (British rock band) concert and a third included complaints about a son-in-law", the report said. Out of that 120 million approximately 81000 of them were believed to contain private and intimate messages. On multiple occasions, it contacted local authorities to get the site brokering stolen information taken down.
The BBC noted that it's unlikely Facebook would've missed such a huge breach.
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