System requirements for latest update

I am running a late 2009 iMac with Mac OS 10.8.5 (Mountain Lion) and Norton AntiVirus 12.9 (68).

I keep getting an alert telling me that there is a free upgrade for my product, but I cannot find anywhere the system requirements for this upgrade. I can't even find a new version number specified.

Apparently having the installer check to make sure someone's system can handle an upgrade before it is installed has gone out of fashion. I keep hearing of people installing software because they are prompted to do so only to find out that they can't run the new version after it's installed. In addition, my sister keeps getting alerts that her Norton AntiVirus is at the end of its life, when in her case she has checked and found out that she can't take an upgrade. Those facts don't exactly inspire blind confidence in me about this update.

So . . . will this mysterious upgrade run on my computer as outlined above? If anyone knows how my sister can turn off those repeated end-of-life alerts, I'd appreciate knowing that, too.

Please don't tell me to upgrade my system software unless you are willing to buy me a new Mac yourself.

Thank you.