Hack the Box Invite

You should get a response code of 200 and expand to see more will show you an encrypted string and the encryption type. In this case, it was rot13. Encrypting will tell you to make a POST request to a specific endpoint. In Terminal (I'm on a Mac) I used curl -X and the full web address including the endpoint and got another encrypted string. This was base 64. Decoding it gave me the access to sign up.