HTTPS does not protect websites from vulnerabilities, it just encrypts the communication.
Wordpres have been vulnerable to XSS a number of times before but the latest release does not have any public ones, also the plugins used on wordpress websites can introduce vulnerabilities.
As for hooking users to beef through XSS, that is covered in the course, did you get there yet?
So to discover vulnerabilities for all of the ones covered in this course you should test every possible method to pass data to the web server, so:
1. send data through input boxes.
2. Send data through file?var=DATA.
3. Interceptor requests using bird as shown earlier and passed data this way.