I think it may be something to do with this command:
I can't be certain, but it rings a bell, and apparently it is a fix for a number of issues.
However, I'm not sure how to apply it because there was more to it than just this.
I ran the command anyway, but it wasn't recognised, though chrome loaded with an oops page.
I think I had to get something first
I found this post:
I've checked and I already have adobe flash plugin installed, but I have no version of pepperflash to disable.