Be careful of Firefox extensions. There has been a vulnerability identified in some of the Firefox extensions, particularly the Google Toolbar. You can read the story by Washington Post Columnist Brian Krebs, "A New Vector For Hackers -- Firefox Add-Ons"
Google has since announced a fix for the security flaw that was identified by Chris Soghoian, an Indiana University doctoral candidate. He has documented many flaws in many of the popular add-ons.
Just be careful when you are updating extensions. Especially if you do it at a public hotspot.