It&#x27;s a security risk, some sites relying on this will be affected by malicious content on sites they link to, so at the very least they&#x27;ll now have to add one of the 2 limiting rel attributes on links that do not require the misbehavior to function.<p>Thanks to the bright and sensible handful of people who add extra cruft to HTML after a brief exchange on a mailing list 3 years after a problem was reported, the other 99.9% of the websites will have to be modified too.