This is why you don't break abstractions. If I'm a user I expect the clipboard to only change when I press ctrl+c or right click -> copy. These should be authoritatively controlled mechanisms that untrusted programs cannot override.

Going further, I want whatever I copy to be whatever I see when I hit copy. Which of course isn't possible in the interactive web.

But unfortunately devs for the last few decades think they can just leave everything undefined and change its meaning for their ad-hoc purposes every minute then claim computing is hard.