I'm not sure how addons can bypass V2 reCAPTCHAs as they operate from iframes and JavaScript can't acces cross-domain content to, ie, click buttons, access urls

I'm not sure how addons can bypass V2 reCAPTCHAs as they operate from iframes and JavaScript can't acces cross-domain content to, ie, click buttons, access urls, or interact with forms. Nonetheless it seems to work, so maybe addon JavaScript is more privileged than developer-console JavaScript. I've seen some v3 reCAPTCHA solvers, such as pyPasser, but I don't understand how they work. They seem to use a hard-coded constant to perform a replay attack to get a token which is guaranteed to succeed ie generate a high score. But... that can't be possible, can it?