When I created this blog using WordPress ver 4.7.4, I just noticed that all external links that open in new window now set with “rel=noopener noreferer”. Whoa. Where have I been all this time! Here is an explanation why we should use “rel=noopener” when we put links especially if it’s opened in new tab/window.
More details could be found in this article from Mathias Bynens.