I have had the same problem: after being repeatedly insisted that I had to update my Flash Player I did and it silently installed McAfee Security Scan Plus. No checboxes, no prompts, nothing. Automatically with Flash Player.
This unethical intrusion is completely unacceptable.
In addition when I tried to uninstall it has been a very big problem: first the uninstall program in the Start meny did not work (it said it cnnot find the program). Then the windows utility in the Control Panel did not succeed neither.
Finally I tried what is suggested in this post:
It seems it worked.
This shows that Adobe is not a trustable company.
I think that the best we can do is move to HTML5 functionalities and forget about Adobe Flash.