The passwords of variant Facebook users were accessible by up to 20,000 workers of the social network, it has been reported.
Security researcher Brian krebs broke the news concerning data protection failures, which saw up to 600 million passwords keep in plain text.
The passwords that were exposed could date back to the year 2012, he said.
In a statement, Facebook said it had now resolved a “glitch” that had stored the passwords on its internal network.
In a detailed expose, Mr Krebs said a Facebook source had told him about “security failures” that had let developers create applications that logged and stored the passwords without encrypting them.
Commenting on Mr Krebs’s story Facebook engineer, Scott Renfro said an internal investigation started after Facebook had uncovered the logs had not revealed any “signs of misuse”.
In comments, Facebook said it had discovered the issue in January as part of a routine security review.
And its investigation showed that the majority of the folks affected were users of Facebook lite, which tends to be used in nations where net connections are sparse and slow.
“We estimate that we will notify hundreds of millions of Facebook Lite users, tens of millions of other Facebook users, and tens of thousands of Instagram users,” the company told Reuters.
But it added it would enforce a password re-set only if its taskforce looking into the issue uncovered abuse of the login credentials.
The news caps a long period of trouble for Facebook over the way it handles and protects user data.
last year September , it said information on 50 million users had been exposed by a security flaw.
And earlier in 2018 it disclosed that data on many users had been harvested by data science company Cambridge Analytica.