Creating a working exploit for the CVE-2012-0002 vulnerability is not trivial, Microsoft security engineers Suha Can and Jonathan Ness said in on Tuesday. "We would be surprised to see one developed in the next few days. However, we expect to see working exploit code developed within the next 30 days."

However, an exploit appeared earlier Friday on a Chinese file hosting website, and its creator is most likely Microsoft itself, Auriemma said. "The executable PoC [proof-of-concept exploit] was compiled in November 2011 and contains some debugging strings like MSRC11678, which is a clear reference to the Microsoft Security Response Center (MSRC)."

Furthermore, the exploit sends a special packet that is identical to the one the researcher included in his report to ZDI (Zero Day Initiative), a program that pays researchers for vulnerability reports and later shares the details with the affected vendors. Auriemma is sure it's the same packet because it contains unique elements that he added to it.

The researcher believes that Microsoft created the exploit for internal testing and then shared it with other security vendors through its Microsoft Active Protections Program (MAPP) to enable them to create attack and malware signatures.

The file might have been leaked by one of those companies or by a Microsoft employee, either directly or indirectly, Auriemma said. There is also the possibility of a hacker stealing it from Microsoft, but that's unlikely, he added.