pen testing https portal?

has any ever tested a https portal?

basically i have a client who has constructed a https portal to all works logon on from anywhere and access apps and files.

how it works is the username and pw are the users AD logon details, the pin is emailed to the user, so for example when the user logs on he has a button saying generate pin!

now say for example he has a pin of 1234 when hits generate pin a picture comes up like this


so the user find his 1st number in his pin, and types the number below it, same with 234 and enters that into the pin field:

username: bloggs
pw: password
pin: 0192

the pin is one time unique! has anyone ever come across a setup like this?

sorry for the long post!

hope you can help!

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