Recently, Hacking Team (a team of hackers which help governments to monitor and hack their citizens) has been hacked and some (at least 3 at the time of this writing) Flash player 0day expolits by Hacking Team were disclosed. Flash is now considered as vulnerable for all systems as it has no fix at the moment.
Firefox has been disabled the Flash from being played unless you enable it. How to watch Youtube videos? I suggest you to install "Youtube Flash-HTML5" add-on if you are using Firefox. You can enable Flash or HTML5 at anytime.
That's all! See you.
UPDATE
According to Google Project Zero, Flash v18.0.0.209 is also vulnerable.
