I tried this on google-chrome and it opens new tabs endlessly. Had to remove Tampermonkey to get it to stop.
I'd keep this one in Firefox land.
For some inexplicable reason, the source code is looking at password fields. This is unnecessary, and raises red flags for me. I will not use this script.
It also looks like it probably depends on a password field existing to work. A lot of forms may not have password fields.