I ask that you consider removing the ability to change html content from Firefox.
If you did this it would help prevent scammers carrying out their online refund scams where they talk victims into giving them access to their computer, have the victim log into their bank account claiming it is to 'connect their bank with the refund server', blank the victims screen while they create a dummy transaction taking advantage of Google Chrome's ability to edit the html to make the victim think they have been given too much money back (when in fact no money was ever exchanged) all to get the victim to buy the scammers Google Play cards or something similar.
By preventing the browser from changing html content you would prevent scammers from using your software to carry out these heinous crimes.
Demonstrated here