CNN News:脸谱网再曝重大安全事故 5000万用户账号被入侵

Facebook is trying to figure out how to deal with its worst hack ever. The company says a security issue has affected almost 50 million accounts.
Facebook's engineers first noticed something unusual on September 16. It took them 11 days after that to stop it.
The hack involved a vulnerability in Facebook's code. Something in the sites' "View As" feature, which lets users see what their Facebook profile looks like to someone else. It allowed hackers to steal digital keys that could be used to take over people's accounts.
What has Facebook done about it? It's temporarily shut down the "View As" feature, and it's reset the digital keys of the nearly 50 million accounts affected, plus 40 million additional accounts.

What we don't know is what the hackers wanted, how long they had access to people's information and whether they took any of it. Best-case scenario, the hackers might not have realized what they did; they might not have actually stolen any info. Or if they did, they don't plan to do anything with it.
Worst-case scenario, they could use the info to blackmail people. They could post user's private messages and pictures online for the world to see or they could use the information to try to influence events like future elections.
Again, experts don't know what or if there'll be consequences to the hack.