How to access iframe using chrome extension?

Question

Yandex

The bottom line is this, I'm writing an extension for chrome. There was a need to get the document code from the iframe, I don’t know how to do it, the following error occurs: "Uncaught DOMException: Blocked a frame with origin " https://toloka.yandex.ru " from accessing a cross-origin frame. HTMLInputElement.check (:27:36)".

I understand that you can't just get to the iframe, but can't a chrome extension do this?
PS I write the script on marimoz scripter.