String encoded XML inside XML, need to parse it into message

Hello, we have a 3rd party sending us information like:

<ns0:foo><content>&lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;?&gt;&lt;

{lots more escaped XML here"}

</content>

</ns0:foo>

What is the best way to parse this internal content into a message type?