TechCrunch reported a major flaw in Facebook Chat today that, in the settings using the "Preview My Profile" feature the way someone else would see it, would expose pending friend requests and even more important, your personal chat messages with friends.

Courtesy: TechCrunch

This bug has come to Facebook's attention who then posted details of the bug on their Facebook. They briefly also disabled use of Facebook Chat and began work on fixing this bug. Facebook then responded to TechCrunch's originally report with the following statement confirming their process in the fix:

For a limited period of time, a bug permitted some users’ chat messages and pending friend requests to be made visible to their friends by manipulating the “preview my profile” feature of Facebook privacy settings. When we received reports of the problem, our engineers promptly diagnosed it and temporarily disabled the chat function. We also pushed out a fix to take care of the visible friend requests which is now complete. Chat will be turned back on across the site shortly. We worked quickly to resolve this matter, ensuring that once the bug was reported to us, a solution was quickly found and implemented.