Starting with a direct link to this post, click on the "Please see this article for more information" link above. Then click your browsers back button. You remain on the "Now running Drupal 8, in the most hipster way imagined." post instead of returning to this one.
There should be some checking of internal / external or absolute / relative URL. This happens when the click of an internal URL with an absolute path is hijacked.
Original bug report: