Private chats between some Facebook users were briefly viewable by other users on Wednesday, an embarrassing technical glitch for a company facing growing criticism over “sloppy” privacy protection. Techcrunch, a blog, first reported a bug related to a feature on the fast-growing social network site that allows a user to see how their profile will appear to other users. By manipulating the “preview my profile” feature, Facebook said people were able to view their friends’ private chat messages and pending friend requests for a limited amount of time on Wednesday. Facebook’s instant messaging service was disabled while engineers fixed the bug. The problem was resolved by Wednesday afternoon, Facebook said. The snafu is embarrassing to Facebook, the world’s No.1 Internet social network with 400 million users, as it comes under increasing scrutiny from privacy advocates. Facebook changed the way users’ personal profile information is treated last month. It now requires that data about an individual’s hometown, education and hobbies be tied to public pages devoted to those topics. Four U.S. senators wrote to Facebook Chief Executive Mark Zuckerberg last week taking issue with some of the changes.