No, you don’t need to do anything. Your copy of Firefox will automatically download and install (probably already has) all security updates. A major update was sent out two or three days ago.
Thank you. This stuff really worries me more now because this year, for the first time, I have had 2 trojans that were a royal pain to get rid of. It seems to me that there has been an uptick in that stuff, but it may also just be that I’ve gotten dumber and somehow am not being careful.
Only if Firefox is set to download updates automatically. That option can be turned off. Please don't give advice like that unless you know how the person's computer is set up.
brytlea -- in Firefox, go to Help -> Check for Updates, and see what it tells you. If it says no new updates are available, you're up-to-date. Otherwise, you might need to download an update.