According to a TechCrunch Europe report, the gaping security security on the Facebook site allowed any user to view the live chats of their friends with just a few mouse clicks. The irony is that the exploit is enabled by the way that Facebook lets you preview your own privacy settings. In other words, a privacy feature contains a flaw that lets others view private information if they are aware of the exploit. The company pulled the live chat feature off line for maintenance
Source: https://threatpost.com/facebook-security-hole-exposes-live-chat-private-data-050510/73926/