<script>$=%27XSSPOSED%27,alert%28$%29<%2fscript>?

It's messed up by the use (and worse, incorrect use) of HTML "character entities" for the single quotes, parentheses, and the forward slash.  It's intended to be

<script>
$='XSSPOSED'
alert($)
</script>

In addition to translating %27, %28, %29, and %2F, I've removed the comma between 'XSSPOSED' and alert($).  The semicolon is the correct statement separator in Javascript.

If you say so, mate.

This is a bot...