It depends on which 'plugin type' you are referring to
1) if you are referring to NPAPI or PPAPI then it might be relatively simple.
2) if you are referring to the one integrated into the Operating system, then you might have to uninstall the windows update as those are pushed out by Microsoft, however if you are on home version of Windows 10 then that update will be forced back down with you having no control unless you literally jump through hoops to prevent it.
3) if you have no idea which version, then i suggest you run this official adobe uninstaller on this page Uninstall Flash Player for Windows
and download an older version from this page( You are going to have to research and use google to determine which version is best for you) Archived Adobe Flash Player versions
You really should provide additional information such as browser as that is extremely important, as well as the operating system architecture ( use google )
Thank you Carm01 for your answer and sorry to have been so vague in describing the problem.
I was talking about the ActiveX for IE11 under Windows 8.1
As you wrote in 2) we just have to uninstall Windows update KB3132372 and refuse that update in the future.
I wish you a happy end of year and more for the next !