Going back to the original question, it's hard to say given how little information about the extension was shared. I think Uladzimir's guidance is pretty solid. My first though on seeing that "The UI of this extension is actually in an Iframe" was the policy he called out.
The main thing I wanted to comment on, though, was the iframe's URL being
http://myapp.com/?URLofCurrentTab. My first though on seeing the URL of the current page in the iframe's URL is immediate suspicion of data harvesting or misuse. There are legitimate reasons to send URLs to remote servers, but A) I don't see an obvious reason to do so given what has been shared so far and B) including sensitive information in query parameters is not good practice. On the security side, a better practice in this case is to postMessage the URL to the iframe, to make your site externally connectable so the extension and sure can communicate directly with each other.
Simeon - @dotproto
Chrome Extensions DevRel