recently i noticed logging into vanguard that if I use firefox autofill password, vanguard always says my password is incorrect, but typing it manually it works. I could clear my password from firefox, type it correctly and login, select "remember my password", log back out and back in, and then have it rejected.

so I figured that the way to make it work is to have it autofill, then select my username and press space then backspace, which is a no-op. That way, the javascript knows i've entered something, and then it works.