Clickjacking

Next, the attacker adds a transparent div on top of the iframe, with a higher z-index...

www.k1tt3ns.com/vacuum-revenge
Watch This Kitty Get Revenge On A Vacuum Cleaner In The Cutest Way Possible
A cat being scared of a vacuum cleaner
An iFramed Website With Overlay
<html>
  <head>
    <style>
      body {
        position: relative;
        margin: 0;
      }

      iframe, div {
        border: none;
        position: absolute;
        width: 100%;
        height: 100%;
      }

      div {
        z-index: 100;
      }
    </style>
  </head>
  <body>
    <iframe src="www.kittens.com/vacuum-revenge">
    </iframe>
    <div></div>
  </body>
</html>