A Firefox plugin called Firesheep has highlighted vulnerabilities in network security by enabling easy capture and exploitation of users' HTTP session cookies over insecure connections, which can lead to unauthorized account access on various services. GitHub was initially vulnerable to this type of session hijacking but has implemented a secure solution involving a second, secure cookie that is only sent over SSL requests, providing an additional layer of protection by ensuring that sidejacked session cookies cannot be used to access sensitive information. This secure cookie is a checksum of the user’s ID and password hash combined with a secret salt value, verified against subsequent SSL requests to confirm authentication. While GitHub has strengthened its defenses, the broader problem of sidejacking persists across many sites, leading to recommendations for users to encrypt all connections, with tools like SheepSafe offering solutions for secure browsing.