A developer out there has released a Firefox extension that will strike fear into folks who often frequent places with public Wi-Fi. The Firesheep extension is capable of sniffing out and stealing cookies of popular sites such as Facebook and Twitter by latching onto the browsing sessions of other users on the same Wi-Fi hotspot. It’s a proof-of-concept extension, but it’s up for download, supporting popular sites such as Facebook, Flickr, Amazon, Dropbox, Evernote and many more. When using it, you can easily intercept a session on a public hotspot and start browsing the site as if you’re that person. This extension was released to force popular sites to send data via the more secure HTTPS protocol, which encrypts its data as its sent, though it comes at the expense of speed. In case you’re thinking of giving this extension a test drive at the nearest Starbucks, you’ll need to make sure that you’re using a wireless card that’s capable of running in promiscuous mode.