As a precaution to such tactics like, I have (long time ago) switched for Firefox Portable, which updates properly, and also backup up its folder and keep a backup of all add-ons .xpi files, (winrar for Windows has a nifty naming mechanism that you can add YYYY-MM-DD HH-MM-SS on the backup name), so if there is an update I don't like, or if after an update I am left with half my add-ons being disabled due to incompatibility, I roll back and stay there for a couple more months till either my add-ons work, or I find and alternative.

Mozilla is far more honest than Google, but better safe than sorry.