Here is a very simple but working XML plugin :
<?xml version="1.0" encoding="iso-8859-1"?>
<listing>
<name>Latest News for a specific category</name>
<query>SELECT id, title FROM #__content WHERE state = "1" AND sectionid = "XXX" AND catid = "XXX" ORDER BY created DESC</query>
<htmlline>
<table>
<![CDATA[
- <a href="index.php?option=com_content&task=view&id=%s&Itemid=XXX>%s</a><br />
]]>
</table>
</htmlline>
</listing>
XXX need to be replaced by your own configuration !
Arnaud