This indicates an attack attempt to exploit a remote code-execution vulnerability in Microsoft XML Core Services.
The vulnerability results from insecure code in the DLL responsible for parsing
nested tags in XML files. It can be exploited via a crafted web page or an HTML e-mail, leading to remote code execution.
Microsoft XML Core Services 3.0
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the patch, available from the vendor's web site: