Cybercriminals have published private messages obtained from 81,000 Facebook users’ accounts, including intimate communications between two lovers.

The hackers were using these private exchanges as the lure in an illicit sales pitch. The criminals claimed to have obtained details from 120 million accounts, which they were offering to sell for 10 cents per account, though that claim appears to be bogus.

Facebook became aware of the website hawking information from user accounts and started investigating about a month ago. On multiple occasions, it contacted local authorities to get the site brokering stolen information taken down.

Meanwhile, the company’s investigation found that users had downloaded malicious browser extensions that allowed hackers to gain access to their information. The infected software gave cybercriminals access, not just to Facebook details, but to users’ activity across any of the online services they use.

It doesn’t appear that Facebook accounts were directly compromised. Nor is there evidence that information for 120 million user accounts had been obtained — the kind of sizable breach that would hardly escape notice.

Guy Rosen, Facebook’s VP Product Management, said the company has contacted browser makers to ensure the infected extensions are no longer offered for download in their stores. It also publishes a user guide, urging people to refrain from downloading software from untrusted sources.

“We encourage people to check the browser extensions they’ve installed and remove any that they don’t fully trust. As we continue to investigate, we will take action to secure people’s accounts as appropriate,” Rosen said in a statement to Deadline.

The attacks, first reported by the BBC Russian Service, were focused heavily on users in Central and Eastern Europe, with minimum focus on people in the U.S.