All the phone numbers in your phone are now on Facebook, warns an alarmed statement making the rounds on the social network, and the numbers are there whether you've allowed the site access to them or not.
That's not exactly true, Facebook argues, noting that the feature has existed for over a year. But users, just now realizing the sensitive information they're sharing, are buzzing up a storm. And for some people, it's one sting too many from a company they're growing reluctant to trust with their data.
"That might be the last straw," wrote one worried Facebook user.
"All my friend's personal phone numbers are on there! Not happy," another complained.
Facebook adamantly denied that the confidential phone numbers of friends and family are freely accessible online, as many have worried. The company posted a statement to its site at the end of the day to address user concerns.
"Rumors claiming that your phone contacts are visible to everyone on Facebook are false," reads a response the company has posted to its website. "Our Contacts list, formerly called Phonebook, has existed for a long time. The phone numbers listed there were either added by your friends themselves and made visible to you, or you have previously synced your phone contacts with Facebook."
"Just like on your phone, only you can see these numbers."
To see the phonebook that's causing all the fuss, click on Account in Facebook's top right corner, then click on Edit Friends, and click Contacts at the left side. Indeed, Facebook does store a list of phone numbers, both contacts you have imported from your phone as well as information your Facebook friends have themselves added.
And that may even be a handy tool, pointed out Don Debolt, director of threat research for Internet security firm Total Defense.
"In some ways, Facebook is attempting to be very helpful," Debolt told FoxNews.com. The site syncs information from your phone to help you find new friends and connect with them, one of a variety of handy features in the social networking toolbag.
"But how exactly they are using this information isn't exactly clear," Debolt noted. "We don't know how our data is being used, we don't know how our data is being monetized."
The real concern for many is the world of underage children on Facebook -- as many as 7.5 million kids under the age of 13, despite the company's official prohibition on those under 16, and 5 million under the age of 10, according to one recent survey.
"I think this is a wake-up call for sure for parents to get involved," Debolt told FoxNews.com. "Teenagers that have Facebook accounts and mobile phones? Their numbers are being shared openly as well."
Children using social networks are far more willing to accept friend requests from people they don't know, even random strangers, warned Noah Kindler, founder of Social Shield, an online monitoring service that helps parents keep track of their children's online activity.
"They don't realize that the same rules that work offline -- don’t talk to strangers -- apply online as well," Kindler told FoxNews.com. Parents simply peering over a child's shoulder every few minutes isn't good enough, he advised. Yet that's all too many parents do.
A new survey conducted by NPD Data and Comscore for Social Shield found most parents admitting that they don't have the tools, knowledge or time to properly monitor their children on social networks -- and many admit that they take no precautions at all.
And those phones busily syncing phone numbers to every member of the social group? About 30 percent of kids have smartphones, the survey found.
"By 8 or 9 years old, 30 to 40 percent of kids have a cellphone," Kindler said.
Many parents use the controls built in to their computers to monitor their children's activity. That's not good enough either, advised Torben Mottes, director of product management with Social Shield.
"Parental controls don't give them what they need to monitor social networks other than to know that their kids are on it," he told FoxNews.com
Ultimately, it's up to us to know where our information is going, Debolt warned.
"This is an example of the diligence we have to take upon ourselves as we're using new technologies to understand how our data is being used," he said.
Jeremy A. Kaplan is Science and Technology editor at FoxNews.com, where he heads up coverage of gadgets, the online world, space travel, nature, the environment, and more. Prior to joining Fox, he was executive editor of PC Magazine, co-host of the Fastest Geek competition, and a founding editor of GoodCleanTech.