According to them, they have detected a bug that displayed user’s contact information to other users who use the “Download Your Information” tool. It was said that when a user use the DIY tool, instead of getting only their own uploaded contact information from the site, they also get, specifically, some phone numbers and emails of people that was connected to their account – therefore, their virtual or online friends.
On the other hand, Facebook stressed out that the information that comes along with the downloaded information has a very high chance that it is not accurate. Thus, it could be that, it does not directly point out a specific user of that gathered contact information. So, evidently, it may not be that dangerous after all.
Moreover, they also reiterated that this glitch was actually reported at the early part of this month but they never receive any report from any Facebook users that concerns the issue. Nevertheless, the company advised that they have already fixed it and all affected users will receive a mail that will explain the matter.
Source: c|net