I'm writing a Chrome extension that needs to alter a popular web app when loaded. Unfortunately, most of the UI of that web app is rendered inside an iframe, and although the address of that iframe matches my content_scripts match declaration, the user script only gets invoked for the top frame.
Q: Is there a method of accessing HTML rendered inside an iframe from a Chrome content script extension? If yes, what permissions and other manifest options should I specify? Thanks.
I've resolved the problem. The following option has to be specified in the content_scripts section of the manifest.json: "all_frames": true. Without it, the script is only applied to the top frame.
// Sometimes one just has to RTFM carefully.
Even "all_frames": true doesn't seem to help in the case of iframes without @src. This is discussed in the bug http://code.google.com/p/chromium/issues/detail?id=20773, which also covers some workarounds, including getting the contentDocument of the iframe element in the source page, e.g. $('a', $($("#canvas_frame")[0].contentDocument)).
This bug is not exactly the problem you were having (you wanted to load your content script inside the iframe, not interact between the iframe and the outer frame) but I think that most people who have one of the problems will have the other one as well.
来源：https://stackoverflow.com/questions/3937355/accessing-iframes-from-a-chrome-content-script-extension