What version of Mac OSX is safe now?

I have just heard that thanks to some sloppy coding (I believe NSA have been asking OS companies to slip in some vulnerabilities, so that it is easier to spy on people), Macs are now vulnerable to hacking attack. It means that when going onto a secure site, the encryption is actually turned off, so that hackers can gain access. I went onto a Mac because I knew Microsoft was pulling the plug on XP, and I really cannot stomach Vista, 7 or 8, and haven't yet had the courage to take the plunge into Linux, although that freeby Mint CD is looking tempting.

Apple has issued a patch for Lion, Mountain Lion and Mavericks, but not Snow Leopard which 20% of macs are on. The problem is that Snow Leopard, like Windows XP, is considered far superior to any of their successors. Something very seriously bad has gone wrong with software writing in the last few years, and it seems to be a trend everywhere. However, even though Snow Leopard is 8 years younger than XP, they have withdrawn security patches on it since last September. XP itself loses its security patches in April.

Mavericks was hailed as Snow Leopard brought up-to-date, but I have been reading horror stories of it trashing external hard drives, running Safari and Finder to a crawl with the eternal spinning beach ball, and being generally bloated and unfriendly. It also insists of transferring things over to a cloud server, which a user has no control over. Losing Quick Time in favour of iTunes is also a great no-no. I'd also have to buy another copy of Parallels Desktop, because PD8 doesn't work on Mavericks, and I use it to run XP and all my beloved legacy software that later versions won't let me run.

Is this unpatched SSL bug only affecting Safari? If so, can I still browse safely on Firefox for now?