You might want to think twice before logging into your favorite websites when using an open Wi-Fi network. A new Firefox extension shows just how easy it is to snatch browser cookies sent over insecure connection for sites such as Facebook and Twitter, allowing malicious users to log into the same website via a process called HTTP session hijacking -- also known as sidejacking. The extension, Butler says moderately knowledgeable hackers were already exploiting this vulnerability, but by making it dead simple to use he hopes to raise awareness and compel sites to raise the bar on security. He also promised to release a new blog post in the next few hours that will help users protect themselves.