I would like to hide elements which have a specific attribute inside an iframe. For example, I want to hide all elements with attribute load-ads-json-from, and there is an element <div load-ads-json-from='//ad.server.net/some/resource'> inside an iframe <iframe src="https://content.server.net/where/the/content/is">.
So far I've tried ##iframe > [load-ads-json-from], or simply ##[load-ads-json-from]. Both don't work. I can conditionally hide the <iframe /> entirely, based on its src attribute, but there is useful info in the page that should not be hidden altogether.
Is there a way to do this?

