If you ascertain Flash is actually required, make sure to fetch it directly from Adobe, don't click through any links you cannot see clearly.
If Flash is legitimately needed for a video, the placeholder for the video will say that Flash is required usually quite simply, 'plugin missing' or similar, possibly with a 'jigsaw puzzle piece' icon. Warning: Do not fall for any pop up telling you Flash is needed or out of date - they're scams, malware. Get the uninstaller from Adobe - Uninstall Flash Player | Mac OS If you don't have it you will see a clear indication if it's required. I'd start by uninstalling Flash completely - very few web sites use it any more.
