Firefox Addons and banking
I recently began to worry a bit about using the same Firefox instance for banking as I do for normal browsing. This is mostly because I have installed around 20 Firefox Addons. Some Addons such as NoScript install updates every couple of days so it's really practical to review the code to see if anything sinister has been included on each update.
Fortunately, you can have separate instances of Firefox running simultaneously. Just run Firefox with the "-no-remote" option. That stops Firefox from connecting to the Firefox profile that is already running.
To do this on Windows, right click on the Firefox icon, Click on Properties, Click Shortcut, add "-no-remote -ProfileManager".
Then check if any Addons are included by looking at "Tools->Addons" (e.g. Ubunty includes a couple by default).
As a bonus clear your cache every time Firefox restarts. Go to Tools->Options->Private Data and tick "Always clear my private data when I close Firefox". Look under Edit->Preferences for this option on Linux.
Doing this doesn't make you totally safe but it does reduce the risks inherent in using third-party Firefox AddOns without having suspend to your normal browsing.