Iframe nesting problem

[Soloralunhwl]

Describe the bug

A clear and concise description of what the bug is.

i want get picture want.png it works when html struct in ： <iframe> aaaaa</iframe>
use testSecond.html
but it look like not work when html struct in ： <iframe> <iframe> aaaaa</iframe></iframe>
use test.html

[Soloralunhwl]

test.docx
@mrcoles