@sanjaykdragon I disagree, this is a VERY GOOD program to help people check and see if their password is not strong. I'm assuming you said that because you could not make a program so good.
This does not work on any browser with proper popup protection. (Firefox prevents popup windows from showing unless specifically allowed by the user.)
It will slow down the tab for a short time until Firefox displays a message that the webpage attempted to open more than 100 popups.
No significant damage or harm.
You should use hashing to secure your login credentials instead of plain text.