All versions of the Flash plugin have been disabled (blocklisted) by Mozilla because of disclosed security vulnerabilities in the plugin that Adobe needs to address via a security update.

• https://support.mozilla.org/kb/why-do-i-have-click-activate-plugins
• https://helpx.adobe.com/security/products/flash-player/apsa15-04.html

• bug 1182751 - (CVE-2015-5122) Blocklist vulnerable versions of Flash Player plugin (18.0.0.203 and lower)

Please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html

• [/forums/contributors/711412] Hacking Team and Flash and Java 0-days!

Sorry for the inconvenience. If you are not accustomed to using the "Ask to Activate" feature for a plugin, here's what to expect:

When you visit a site that wants to use the Flash, you should see a notification icon in the address bar and one of the following: a link in a black rectangle in the page or an infobar sliding down between the toolbar area and the page.

If you see a good reason to use Flash, and the site looks trustworthy, you can go ahead and click the Lego-like icon in the address bar to allow Flash.

But the page might be using Flash only for tracking or playing a video ad. If you don't see an immediate need for Flash, feel free to ignore the notification, it will just sit there in case you want it later.