Hundreds of millions of Facebook account passwords were stored in plain text and searchable by thousands of Facebook employees going back as far as 2012. Facebook found the problem in January, but just went public with it on Thursday.
Security experts are urging users
to change their passwords immediately.
"As part of a routine security review in January, we found that some user passwords were being stored in a readable format within our internal data storage systems. This caught our attention because our login systems are designed to mask passwords using techniques that make them unreadable. We have fixed these issues and as a precaution we will be notifying everyone whose passwords we have found were stored in this way."