This is hardly new...

https://lifehacker.com/how-to-navigate-away-from-a-website-t...

I've always gotten around it by Long pressing the Back button and then selecting the page to go to. Bypassed your "block" as well...

This is not a big of a find that you think there is. And I'm not sure calling it a "Zero Day" is appropriate either as it doesn't exactly cause much of a problem.

Also does not work with uBlockOrigin disabling javascript (either of uBlockOrigin's global block or inline script block prevents it from working).

Right click on the back button will show you a list with the previous pages. Looks like it doesn’t affect it.

This is not a zero day, disabling the back button is a commonly employed technique on some sites.

You can't use the back button to leave a page