Reference:
I'm still on 3.5 should i just leave it for the moment.
AS far as I know, the security problems were with v 3.6, but only Mozilla could confirm that for certain. So I guess you don't need to download v 3.6.2, but I would have thought it was advisable as you would then have the most upto date version, and if Mozilla release any further patches they would be concentrating on the current version reather than older versions.