If your Mac has recently told you that Adobe Flash Player has been disabled, or if you have discovered that it no longer works, this is because of a very recent change in the permitted plug-ins for El Capitan, Sierra, and High Sierra, as set by XProtect. Apple has silently updated XProtect, in the course of which it blocks the use of all versions of Flash Player older than the latest release, version 18.104.22.168.
You can download the Flash Player update from here. Once installed, it should work normally again.
What is slightly odd about this is that this latest version hasn’t, according to Adobe, had any security fixes from the previous release, 22.214.171.124, so it isn’t clear why Apple has made version 126.96.36.199 the requirement, rather than 188.8.131.52. But you can’t argue with XProtect.