Facebook bug exposes contact information of 6 million users

Facebook bug exposes contact information of 6 million users
A Facebook User Operations Safety Team worker looks at reviews at Facebook headquarters in Menlo Park, Calif. (AP Photo/Paul Sakuma, File)
Facebook says a bug in its system led 6 million users' contact information being inadvertently exposed.

The social media company said Friday that a bug led to some contact information — such as email addresses or phone numbers — to be uploaded by other users.

The problem arose when a Facebook user downloaded an archive of their Facebook account through Facebook's "Download Your Information" tool. Because of the bug, the user may have been provided with additional email addresses or telephone numbers for their contacts or people with whom they have some connection.

Because the contact information was provided by other people on Facebook, it was not necessarily accurate.

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

See the text of the e-mail below:

Your privacy is incredibly important to everyone who works at Facebook, and we're dedicated to protecting your information. While many of us focus our full-time jobs on preventing or fixing issues before they affect anyone, we recently fell short of our goal and a technical bug caused your telephone number or email address to be accessible by another person.

The bug was limited in scope and likely only allowed someone you already know outside of Facebook to see your email address or telephone number. That said, we let you down and we are taking this error very seriously.

Describing what caused the bug can get pretty technical, but we want to explain how it happened. 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, the email addresses and phone numbers used to make friend recommendations and reduce the number of invitations we send were inadvertently stored in their account on Facebook, along with their uploaded contacts. As a result, if a person went to download an archive of their Facebook account through our Download Your Information (DYI) tool, which included their uploaded contacts, they may have been provided with additional email addresses or telephone numbers.

Here is your contact Information (inadvertently accessible by at most by xx Facebook user(s):
XXXXXXXX
XXXXXXXXX

We estimate that xx Facebook user(s) saw this additional contact info displayed next to your name in their downloaded copy of their account information. No other info about you was shown and it's likely that anyone who saw this is not a stranger to you, even if you're not friends on Facebook.

We recognize that mistakenly sharing contact info is unacceptable, even if you are acquainted with people who saw these details, and we've taken measures to prevent this from happening again. For more information on the bug, please read our blog post.

All of us at Facebook take this issue very personally. We appreciate your ongoing use of Facebook, and are working every day to deliver the level of service you expect and deserve.

Thank you,
The Facebook Team