There’s a new browser extension floating around that allows you to see the email of any member of LinkedIn at no cost—except your own privacy on the site.

The tool, called SellHack, allows you to “hack into” LinkedIn’s system and reveal the personal email on (almost) any person’s profile. Meaning anyone can grab your email off the site and use it for their own nefarious (or, er, professional?) purposes. No, SellHack isn’t breaking into LinkedIn’s secure systems. It does this, according to its very own blog, by running through an algorithm while you’re on a person’s LinkedIn page. The algorithm checks publicly available data to produce that person’s email address, or at least its very best guess.

The catch is, even after you’ve used SellHack, the extension is able to watch your activity on the site and collect the information of any direct connection whose page you’ve decided to visit. What it’s using this information for is unclear.

The plug-in is compatible with Chrome, Firefox, and Safari and is alarmingly easy to use.

All you need to do is, go to SellHack.com.

Click the blue Install Sell Hack Extension button.

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Choose which browser you’re using.

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Once you’ve picked, click the green button. (Below that button, you’ll see further instructions you’ll need to follow, depending on what browser you’re using.)

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