I've been alerted to a "serious" identity theft threat to Mac users by my bank. I am running OSX 10.6.8. Can anybody tell me if this threat is real and what issues I might expect if I upgrade? An associate upgraded to Mountain Lion and had many issues.

Call your bank for verification. If you received this by email, then be suspicious as it could just be phishing email.

Nothing has been announced by Apple about a vulnerability with Snow Leopard. Contact your bank directly, not through in links in that notification to you refer to and talk with their security people to see if this is legitimate or a phishing attack. There have been a lot of those the past couple of months so talk directly with your bank about it.

Ralph Landry1 wrote:

Nothing has been announced by Apple about a vulnerability with Snow Leopard.

Worth a read:

http://arstechnica.com/apple/2014/03/snow-leopard-updates-are-probably-done-here -are-your-os-x-upgrade-options/

I am unaware of any such threat. There shouldn't be any problem updating to Mavericks. Most problems people report are with incompatible 3rd party software.

OP is referring to the "go to fail" bug.

He can test if Snow Leopard is susceptible to this from one of the test sites mentioned in this article.