How to prevent flash player from updating
For more information, see Why do I have to click to activate plugins?
Mozilla applications are regularly updated for security and stability; however, Mozilla does not provide updates for plug-ins.
If Adobe's test page does not show that Flash is working even though you have installed the latest version, your Flash plugin may be disabled in the Add-ons Manager.
To make sure that Flash is enabled, There are three different types of Flash Players: an Active X version for Internet Explorer, a Chrome version built into the browser and a plugin version for Firefox and some other browsers.
If you want Flash to work in Firefox you must install the plugin version, as explained above.
An "Activate Adobe Flash" prompt on pages with Flash content could either mean that the Flash plugin is set to "Ask to Activate" in the Add-ons manager or that Firefox has prevented an unsafe Flash version from running automatically.
If Adobe's test page says that Flash is outdated and you don't want to wait for the automatic update, you can update Flash manually by downloading and installing the latest version from Adobe.The Adobe Flash Player browser plugin lets you view video and animated content in Firefox.