System Preferences > Flash and you can delete all info there manually, or set it to not accept information.
What I use is the free Firefox web browser + Ghostery and Click&Clean.
Ghostery has a option to delete Flash and Silverlight cookies upon exit (if enabled in preferences)
Click&Clean wipes everything when the browser is closed.
Firefox also has click to play, so Flash and other plugins are not running on every site, rather one has to click to enable it when they want as to prevent those from running and placing/retriving cookies in the first place. Better security also.
And there is more than just Flash cookies, there are web bugs, mouse trackers, history sniffers, HTML and Ever Cookies, plus all sorts of webside exploits.
Only by enabling Javascript/scripts only on sites you trust can you avoid a lot of this nonsense, the only easy method is to use Firefox and the NoScript add-on, which you drag a "temp allow all" button to the toolbar in Firefox to click on sites you trust.
https://en.wikipedia.org/wiki/NoScript
Also Ad Block Plus is also advised, as ad's can deliver makware and slow down the browsing speed.
See this here
Maintain some level of privacy/cookie tracking
