OAuth was first introduced in 2007. It was created at Twitter because Twitter wanted a way to allow third-party apps to post tweets on users' behalf. Take a second to imagine designing something like that today. How would you do it? One way would just be to ask the user for their username and password. So you create an unofficial Twitter client, and present the user a login screen that says "log in with Twitter". The user does so, but instead of logging into Twitter, they're actually sending the...