'Chrome Extension Inject into iFrame with JavaScript

I'm working on a Chrome Extension that allows a user to open a site into an iframe in a new tab. My goal is to allow them to modify the CSS by injecting the code via JavaScript from the parent window, yet I'm getting blocked by origin-only issues.

Is there a way around this? I know I've seen other extensions do similar things.

iframegoogle-chrome-extensionsame-origin-policy


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