Facebook has officially confirmed that a glitch exposed the contact information’s such as email addresses or phone numbers, of 6 million of FB users. The problem stemmed from the Download Your Information (DYI) tool that allows users to upload their contact lists or address books to Facebook so that the social network can serve up friend recommendations or invite people to join Facebook.
Because of the bug, some of the information used to make friend recommendations and reduce the number of invitations that  was  stored in association with people’s contact information as part of their account on Facebook. The company says the bug has been fixed.