The Challenge Response System is a system put in place to help you change your password in the future.
This allows you to login to the Password Selfservice System, even if you can't remember your password.
Click "Forgotten Password" at https://selfservice.ufs.ac.za and follow the prompts to reset your password

You will be asked a series of security questions as shown below.
The answers will be required if you want to reset your password in the future.

After answering all the questions, you'll be presented with the following Dialog:
Click "Continue"
Click Next...