Once again today, this plugin is flaged as vulnerable and Firefox disable it.

Is there any way to turn off this behavior?

IMO If Adobe Flash Player gives so much problems, and its vulnerable version or version, Firefox should remove any support for it and don't work with it anymore.

Usually when you run the installer for the Flash plugin, it replaces what you have in Firefox and everything is good. However, something might have gone wrong in that process.

Do you want to check what version is actually on disk? You can open this folder:

C:\Windows\SysWOW64\Macromed\Flash

There should be one file starting with NPSWF32:

NPSWF32_18_0_0_203.dll

(Windows may hide the .dll extension; you can force Windows to show all file extensions using the method in this article: http://windows.microsoft.com/en-us/wi.../show-hide-file-name-extensions)

If you have an earlier version: You can grab an installer from the following page:

https://www.adobe.com/products/flashplayer/distribution3.html

Choose either the EXE or MSI installer for "plugin-based browsers"

If you already have the latest version: Firefox may not be detecting it for a variety of reasons. However, that list is long so I'll pause here and see whether the previous stuff is useful to you.