The Verge has verified the material is legitimate, and a Microsoft spokesperson tells us that the company is “investigating the matter.”
It’s unlikely that this latest source code leak will pose any significant threat to companies still stuck running Windows XP machines. Microsoft ended support for Windows XP back in 2014, although the company responded to the massive WannaCry malware attack with a highly unusual Windows XP patch in 2017.While this is the first time Windows XP source code has appeared publicly, Microsoft does run a special Government Security Program (GSP) that allows governments and organizations controlled access to source code and other technical content."
Read more on TheVerge.com