Facebook said it became aware of the glitch last week and immediately shut down the feature that was causing the problem.
The glitch allowed users access to email addresses and telephone numbers of Facebook participants through a feature that recommends other members as potential friends within their system.
The email addresses and telephone numbers of 6 million members were temporarily exposed to other members who were downloading address book information, the Los Angeles Times reported Saturday.
Facebook said the damage was "likely to be minimal since any email address or phone number that was shared was shared with people who already had some of that contact information anyway, or who had some connection to one another."
"It's still something we're upset and embarrassed by, and we'll work doubly hard to make sure nothing like this happens again," Facebook said in a statement.