The flash player is the thing that isn’t updated automatically through mint updates, so after some time from system installation it might be quite obsolete.
Go to Adobe site and download recent tar.gz pack of FLASH player for linux.
Extract folder, open it and copy paste the libflashplayer.so file to etc/alternatives overwrite the old one.
That’s it, log in/out or restart browser. Check version with right click on any flash object in the browser. Be happy with new updated flash on your system