I've just run into a pathological case with HTML parsing. I've always thought that a <script> tag would run until the first closing </script> tag. But it turns out this is not always the case.

This is valid:

<script><!--
alert('<script></script>');
--></script>

And even this is valid:

<script><!--
alert('<script></script>');
</script>

But this is not:

<script><!--
alert('</script>');
--></script>

And neither is this:

<script>
alert('<script></script>');
</script>

This behavior is consistent in Firefox and Chrome. So, as hard as it is to believe, browsers seem to accept an open+close script tag inside an html comment inside a script tag. So the question is how do browser really parse script tags? This matters because the HTML parsing library I'm using, Nokogiri, assumed the obvious (but incorrect) until-the-first-closing-tag rule and did not handle this edge case. I imagine most other libraries would not handle it either.

javascript html html-parsing
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