Rofl, finally got this one. I thought it might have been something to do with nested strings but obviously it just doesnt allow you to enter <script> this is a tough one if you think about it too much you will kick yourself when you get the answer. Ill give you one hint for people who still scratch there head. Force it to say script. <sscripts> - See what it does now go from there.
Think of it like this:
SERVER: "STATE PASSWORD AS PRODUCT OF 42"
USER: Answer must be, "8!"
USER: *types an, "8"
SERVER: I FILTER ALL BUT THE THIRD DIGIT
USER: Ah, HA!
USER: *types 12833
SERVER: ACCESS GRANTED