Millions of Facebook Inc.'s user records were inadvertently posted on Amazon.com Inc.'s cloud computing servers in plain sight, researchers at cybersecurity firm UpGuard reported on Wednesday.

Facebook said last month it resolved a glitch that exposed passwords of millions of users stored in readable format within its internal systems to its employees.

Cybersecurity blog KrebsOnSecurity also reported in March that the passwords were accessible to as many as 20,000 Facebook employees and dated back as early as 2012.

Facebook and Amazon did not immediately respond to requests for comment.