Facebook has reported a bug that has led to the exposure of users’ information.

The bug, which attacked the company’s ‘Download Your Information’ tool, left about 6 million users’ contact information (email addresses or phone numbers) inadvertently exposed to other users who either had some contact information about that person or some connection to them. Describing what caused the bug, Facebook said: “When people upload their contact lists or address books to Facebook, we try to match that data with the contact information of other people on Facebook in order to generate friend recommendations.

“Because of the bug, some of the information used to make friend recommendations and reduce the number of invitations we send was inadvertently stored in association with people’s contact information as part of their account on Facebook.”

According to the company, if a person went to download an archive of their Facebook account through our Download Your Information (DYI) tool, they may have been provided with additional email addresses or telephone numbers for their contacts or people with whom they have some connection.

This contact information was provided by other people on Facebook and was not necessarily accurate, but was inadvertently included with the contacts of the person using the DYI tool.

Facebook said it has fixed the problem and is in the process of notifying affected users via email.