Iframe element children are put outside of the inner html/body

[malidukica]

We would like to use an iframe to display some html contents, but the iframe function puts the provided children list outside of the inner html/body (tried wrapping the contents with body/html and still get the elements outside).

Example:

https://ellie-app.com/bCMkrCVpxYCa1

[jhf]

I've tested with Safari 14.0.1 (16610.2.11.51.8) and Firefox 82.0.3, and in both there is no "contents" in the iframe.

Safari

Firefox