http://spywarcbzke2e6skl7wjwtmmnrkslue24cld6kfcufjhhwxtceogmuad.onion/articles/firefox.html
Then, it was Yahoo, which isn't better: "The Yahoo Search History tool allows you to see what you've searched for in the past. ". So it saves all your searches. And deleting does nothing: "Even if you clear your past searches or turn the Search History tool off, Yahoo still collects and stores search user log data when you use Yahoo Search technology."