Shaun Nichols writing for The Register:
Adobe says a buggy installer is the reason some people have two different versions of Flash Player on their Windows PCs.
The software house told The Register it had to create an additional build of the browser plugin specifically for Microsoft's Internet Explorer after the version made for other browsers – such as Mozilla's Firefox and Microsoft's Edge – wouldn't install properly for IE.
So, for example, if you have Internet Explorer and Firefox on your machine, you'll have two slightly different copies of Flash that should be functionally the same.
Quality control? Testing? What's that then?
I wouldn't blame you if you feel that this is the straw that broke the camel's back. Here is how to completely uninstall Adobe Flash from your computer.