Javascript in wiki page executed by {index}

Arbitrary Javascript placed on a wiki page is executed if it is in the "blurb" included in the

page 2 (within same space as page 1) contents:
<script>
alert("We have a problem...");
</script>

Go to page 1. The index, including a brief summary of page 2, should appear. An alert window will pop up. In fact, any HTML will be rendered, so this may lead to additional problems I have not investigated