For anyone curious as to how I solve the problem right now, I just have two separate Firefox profiles. One has a ton of plugins; I use it to browse the web. The other has no plugins; I use it to visit my bank's website.
I use a separate portable FF[0] for that. That makes "cross contamination" impossible.
cp -a /my/firefox/profile/template "$TMPDIR"
firefox --no-remote --profile "$TMPDIR"
Gives you a fresh profile every launch.