Facebook on Wednesday temporarily shut down its online chat feature after a software glitch let people's friends in the online community see each others' private chat messages.
For a "limited period of time" chat messages and pending friend requests could be made visible to friends, according to Facebook.
For peeks at the usually walled-off information Facebook users had to manipulate a "preview my profile" feature in a particular way, according to Facebook.
"When we received reports of the problem, our engineers promptly diagnosed it and temporarily disabled the chat function," a Facebook spokesman said in an email response to an AFP inquiry.
"We also pushed out a fix to take care of the visible friend requests."
Chat was back in action for most Facebook users by 1900 GMT.
The software glitch struck as the world's top online social-networking service is increasingly scrutinized regarding the privacy of its users.
Slightly more than half of adult users of social networks have posted "risky personal information" such as birth dates or children's photos to profile pages, according to a Consumer Reports survey titled "Social Insecurity."
The survey indicated that 23 percent of Facebook's users "either didn't know that the site offered privacy controls or chose not to use them."
Facebook has evolved into an online repository for personal information and the company should protect user data as vigilantly as banks treat contents of safe deposit boxes, said Andrew Brandt, lead threat research analyst at computer security firm Webroot.
"They shouldn't be leaving the vault unlocked even for a few hours," Brandt said, referring to the chat feature glitch.
Internet users need to realize that any information they put online can escape into the wild, according to Brandt.
"If you have embarrassing photos from spring break that could get you in trouble now or in the future, just don't put that stuff there," Brandt said.
"Remember that everything that goes on the Internet essentially stays there. Even if Facebook hides it away, that stuff might be retrievable in the future."
Last week, four US senators expressed concern to Facebook over recent changes to the social network that they say compromises the privacy of its more than 400 million users.
In a letter to Facebook co-founder Mark Zuckerberg, the senators said they worried that personal information about Facebook users is being made available to third party websites.
They also said the Palo Alto, California-based Facebook should make sharing personal information an "opt-in" procedure in which a user specifically gives permission for data to be shared.
One of the letter's signatories, Democratic Senator Charles Schumer, has urged the US Federal Trade Commission to look into the privacy practices of Facebook, MySpace, Twitter and other social networking sites and to issue guidelines on the use of private information.
Facebook on April 21 rolled out a series of new features including the ability for partner websites to incorporate Facebook data, a move that would further expand the network's presence on the Internet.
Facebook vice president of global communications Elliot Schrage has been adamant that online privacy is taken very seriously at the company.
"These new products and features are designed to enhance personalization and promote social activity across the Internet while continuing to give users unprecedented control over what information they share, when they want to share it, and with whom," Schrage said.
Explore further: Who's Who in music streaming: Tidal, Spotify, Pandora & more