Facebook called this ''a glitch''.....
'The passwords were accessible to as many as 20,000 Facebook employees and dated back as early as 2012, cyber security blog KrebsOnSecurity, which first reported the issue, said in its report.
“These passwords were never visible to anyone outside of Facebook and we have found no evidence to date that anyone internally abused or improperly accessed them,” the company said.
KrebsOnSecurity, citing a senior Facebook employee, said an internal investigation by the company so far indicates that between 200 million and 600 million Facebook users may have had their account passwords stored in plain text.'
https://www.nst.com.my/world/2019/03/471874/passwords-millions-facebook-instagram-users-exposed-glitch