My page is an iframe in the main page. And hung a link like <a href="http://www.google.co.kr" target="_blank"> google </a> in an iframe. However, the links do not operate. target = '_ self' is a well operation, target = '_ blank' is not operated. It works fine on the main page.
Why would it?
I'm sure the issue have something to do with the sandbox attribute. It seems that you can add the attribute "allow-top-navigation", change the link to 'target=_parent' and should works.
Here is a little bit of documentation from the MDN:
allow-top-navigation: Allows the embedded browsing context to navigate (load) content to the top-level browsing context. If this keyword is not used, this operation is not allowed.