Fixing Firefox after Stealther Rated 1 out of 5 stars
First, uninstall any version of Stealther you have.
Then find the previous review about removing the entries from prefs.js and do it.
Go to your preferences' privacy, security and advanced/network tabs and set your cookies, history, passwords and cache.
Go to about:config -
Set browser.sessionstore.enabled to true.
Set browser.sessionstore.max_tabs_undo to 10 (the default). This will re-enable your Recently Closed Tabs.
Set network.http.sendRefererHeader to 2. This will re-enable the referrer header which A LOT of finance and banking sites need. I am fairly certain most victims of a Stealther blowup don't even know their referrer function is broken...