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Interested in finding out what information Facebook is sharing about you through the company’s new open-graph API? Developer Ka-Ping Yee has come up with a simple tool that shows you everything the social network sends to anyone whose app or service decides to plug in to the new feature — all it requires is a user ID or user name. You can find out what information you’re sharing via your public profile by looking at your settings within Facebook,too, of course. But Yee’s tool shows you exactly what data a developer would get when it asks Facebook for info via the API, such as your name, birth date, location, etc. and also any public information such as your “likes” (formerly pages you were a “fan” of), your photos and so on.

As of yesterday, the tool was also showing some information that most users had not made public. Yee — a Canadian-born programmer who works for Google’s (s goog) charitable arm, Google.org, and developed the “people finder” tool used after the Haiti earthquake — found that the API was showing what events he had recently attended, and even those he was planning to attend, information he didn’t recall giving Facebook access to (another developer says the old API provided this as well).

Thanks in part to Yee flagging the issue in a blog post and contacting the social network, Facebook now appears to have fixed it so that the API no longer makes this available by default (the developer says that his experiments with the Facebook API were the result of “personal dabbling” and don’t have anything to do with his work for Google).

Even though this glitch has been fixed, however, Yee’s tool has managed to surprise even some of the savviest tech users with what it reveals. Caterina Fake, co-founder of Flickr and Hunch.com, for example, on Twitter called it “immensely useful [and] potentially scary. I’m a sophisticated privacy vet & found things I hadn’t known I was sharing!”

Facebook has come under fire from a number of sources over privacy related to its new features, particularly the fact that users have been “opted in” to services such as “instant personalization,” which allows several sites that Facebook has partnered with to show users personalized content by drawing on their Facebook profile. Four senators sent the social network a letter today complaining about this kind of behavior, one of whom has also written a letter of complaint to the Federal Trade Commission.

Related content from GigaOM Pro (sub req’d): Who Owns Your Data in the Cloud?

Post and thumbnail photos courtesy of Flickr user dirac3000

