An encryption flaw called the Heartbleed bug is already being called one of the biggest security threats the Internet has ever seen. The bug has affected many popular websites and services — ones you might use every day, like Gmail and Facebook — and could have quietly exposed your sensitive account information (such as passwords and credit card numbers) over the past two years.

But it hasn't always been clear which sites have been affected. Mashable reached out some of the most popular social, email, banking and commerce sites on the web. We've rounded up their responses below.

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