Hey guys!
I want to give you a SPOILER FREE "NOT YOUR GOLDEN PILLOW" guide to this mission.
Really quite simple.
1) Learn about javascript injections, and pay close attention to alert functions. Alert functions will display certain things on the page. (I know absolutely NO proper terminology so just bare with me here

) Javascript:alert(document.cookie) will display the cookie that comes with page. (again, correct me if I'm wrong. all I really know is how the mission works but it's like a mute teaching an oral language haha) Now pay close attention to what happens. A window will be displayed showing you the cookie. It's basically calling a system in the page.
2) Knowing this, it's time to look at the source code! woot~
3) once you find what function x= , you have to find what moo equals. This of course shows that moo equals a javascript codec that is illegible with the naked eye.
4)If you take what I said in the first few steps, apply some common sense and logic, then you should have it all together now! If you don't, try this.
(5) javascript:alert(document.cookie) calls a system on the page. What system would you call to display the password? In other words, how does function check x tell you what the password is and what system to use?
HOPE I DIDNT GIVE AWAY SPOILERS!!
Just trying to help :p
GOOD LUCK~
Baron