Have you ever wondered how Mozilla gets paid by the privacy-hating mega-monopolies like Google? Simple; when you use the default search engine plugins that are packaged with the browser, parameters similar to these are added to your search query:

client=firefox
name="appid" value="ff"
name="hspart" value="mozilla"

These parameters inform the search engine that you're using a Firefox/Mozilla product and that's all it takes for Mozilla to rake in millions annually. From my point of view that wouldn't be a problem were Mozilla an ethical company, but in my view that is far from the truth. If you do not wish to support unethical companies like Google, or want to punish Mozilla for doing so (as well as many other stupid things) read on...

To mitigate potential risks to your anonymity posed by the default Firefox search engines, simply disable all of them and use alternatives.