Facebook has announced that it was hacked last month in a short statement on its website. Apparently, a few machines at Facebook HQ visited a compromised developer site.
Here's the full statement from the company. The company declined to comment when we reached out to them.
Last month, Facebook Security discovered that our systems had been targeted in a sophisticated attack. This attack occurred when a handful of employees visited a mobile developer website that was compromised. The compromised website hosted an exploit which then allowed malware to be installed on these employee laptops. The laptops were fully-patched and running up-to-date anti-virus software. As soon as we discovered the presence of the malware, we remediated all infected machines, informed law enforcement, and began a significant investigation that continues to this day. We have no evidence that Facebook user data was compromised in this attack