In about:config, while it lasts -- if it's even available--, try flipping the bool for: dom.event.clipboardevents.enabled To false Edit: my mental molasses d

In about:config, while it lasts -- if it's even available--, try flipping the bool for: dom.event.clipboardevents.enabled To false Edit: my mental molasses delayed my seeing that the feature was removed and that you've moved on. I'll leave the comment though.