Not asking for OS advice, folks.
Ehrmmm.. actually, you are. “Lion”, “Mountain Lion”, and “Yosemite” are all OS’ that run on macs. Other OS’ were mentioned in an attempt to help you.
If your particular set-up is functioning normally then you can probably continue with what you have, especially if this backdoor does not affect you.
If you wish to upgrade beyond what you have now then the rest of the advice in this thread applies, yes.