About six million users of Facebook saw their email addresses and phone numbers exposed by a bug in the Facebook system last week.
“We’ve concluded that approximately 6 million Facebook users had email addresses or telephone numbers shared. There were other email addresses or telephone numbers included in the downloads, but they were not connected to any Facebook users or even names of individuals,” Facebook said.
According to the social network, “For almost all of the email addresses or telephone numbers impacted, each individual email address or telephone number was only included in a download once or twice. This means, in almost all cases, an email address or telephone number was only exposed to one person. Additionally, no other types of personal or financial information were included and only people on Facebook – not developers or advertisers – have access to the DYI tool.” The DYI tool Facebook mentions is the Download Your Information toll which will be discussed later as the social network discussed how the bug came to being.
However, the Facebook says that they have already squashed that bug and users should now have their phone numbers and email addresses they intent to keep private now private again.
“After review and confirmation of the bug by our security team, we immediately disabled the DYI tool to fix the problem and were able to turn the tool back on the next day once we were satisfied that the problem had been fixed,” Facebook said.
“We currently have no evidence that this bug has been exploited maliciously and we have not received complaints from users or seen anomalous behavior on the tool or site to suggest wrongdoing,” the social network said.
It added: “Although the practical impact of this bug is 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. Your trust is the most important asset we have, and we are committed to improving our safety procedures and keeping your information safe and secure.”
Facebook revealed how the bug came to life and this is how the social network explained it.
“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. For example, we don’t want to recommend that people invite contacts to join Facebook if those contacts are already on Facebook; instead, we want to recommend that they invite those contacts to be their friends on Facebook.
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. As a result, 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 that they have contacted regulators in the US, Canada and Europe and are notifying people who were affected by the bug.
Image by Mike Keeling on Flickr (CC)