chromium/third_party/blink/manual_tests/inspector-wrappers/console-alert-object.html

<html>
<head>
<script src="inspector-wrappers-test-utils.js"></script>
<script>
window.alert = function(msg) {
  msg.__proto__.toString = doAttack;
  return msg;
}
</script>
</head>
<body>
<script>instructions({console: true, trigger: "alert({})"});</script>
</body>
</html>