This extension helps you re-use your authentication details for Coursera with the open source coursera-dl software.
This extension can be installed in Firefox or in Google Chrome.
You should now have this icon 
installed in your browser. Click it.
If you are not logged in to Coursera, it will tell you so and ask you to log in.
If you are logged in to Coursera, it will give you an option to copy the authentication code. Click that button, and you can use it as the CAUTH code that is added in this (open) pull request.