This has been happening for a while, since around SRU 18 (IIRC), and has got progresivly worse.
S11.4 - Current SRU24 on x86.
FF - current 68.9.0esr
Whenever I go to a website that requires a user/password combo (like MOS or here), I can enter te username OK. But as soon as I tab to the PW field it hangs and does not allow input.
Soetimes (ie:- Ebay) it eventually allows me to input a PW. At other times I have to kill -9 it.
Safe mode is no different.
I don't see this behaviour on my Mac or Linux options)
Any clues as to where to look, I often still prefer to use Solaris x86 as my desktop.