I don't know, FF is coming close to IE in insecurities...unless your talking about S or O in which case not as many people try to hack those yet. Actually, I use IE64 (aS OPPOSED TO normal IE) because that seems to be more secure than FF and I didn't have to do anything extra to use it on the new browsing computer we have.
In the above case I tried it in both IE64 and IE32 though. I do have a 64 bit processor, but many people do now days...it does throw a wrench in some things.
Is it an FLV file, and if so what was the original file from?