I was looking for a bug in forgot password facebook.
I was send reset password link to my email account through facebook. Open the link and change my id with Mark Zukerberg's Id to 4.
Mark Zukerberg's Id
I was thought that I have fount something. but its not I've tried this bug using my own accounts (Not Mark Zuckerberg :) and it doesn't allow me to set a new password. The "n" parameter is tied to the "u" parameter. Instead of using Mark Zuckerberg's account