Facebook released a statement in a yesterday blog post saying that although hackers managed to brake in they weren’t able to steal any kind of user data. Hackers most likely only had access to the internal employee network and although they could have gained even more access rights from here the hack attack was discovered in time to stop it.
A big mobile developer website was compromised. Via some unreleased exploit code many people, including Facebook employees, had their PCs hacked after visiting this site. The spotting of a suspicious file on one employee laptop triggered an immediate investigation. Company-wide all PCs were checked and Facebook found “several other compromised employee laptops.”