Make sure that you only install Adobe Flash that is downloaded
directly from Adobe. This is the only way to truly guarantee that
it is an Adobe copy and not a malware or trojan carrying copy.
Also, only update either from the Adobe Flash in System Preferences
or download directly from Adobe. If ANY website tells you to download
an update, always check in Sytem Preferences or directly from Adobe
to determine if that is the case. Too many people blindly click yes when
prompted and many end up with various malware on their sytems as
the malicious people make it look very official looking.
As a general rule when using the internet, if you didn't ask for it,
do not accept it!