Microsoft has had to contend with quite a number of major leaks over the last few years, including everything from parts of the Windows 10 source code in 2017 to a Bing app server that recently leaked multiple terabytes of GPS data and user searches for more than week. On top of all that, it appears that a ~43GB archive of Microsoft source code, including the Windows XP (with Service Pack 1) and Windows Server 2003 operating systems, has reportedly leaked, along with a array of older OSes, including a few versions of Windows CE and MS-DOS.
Both Windows XP SP1 and Windows Server 2003 have been EOL for quite some time now. Current estimates put Windows XP’s market share at about 1.26% (and falling). Windows Server 2003’s share among connected servers is even lower and is estimated to be approximately .57% as of today. The source code for those operation systems leaking publicly does technically make it possible for new exploits to be found that could open up systems running the OS to fresh attacks, but in reality, the risk is minimal, for a few reasons.
Nefarious hackers and crackers will typically go after high-value targets and it is unlikely that many high-value targets are still running these aged operating systems. Hackers also tend to go after bigger targets – a combined (estimated) market share of less than 2% is hardly a big target. Finally, the source code for Windows XP has been available to some third-parties for quite some time now. And it is likely that that code has been archived by many entities that shouldn’t have had access. A public leak like this one, is a much more serious issue, of course, but is still unlikely to cause any major problems.
There is a remote chance that the leak reveals new exploits for Windows 10, however. Although Windows 10 is far removed from Windows XP, some of XP’s DNA remains in Microsoft’s current OS for the sake of backwards compatibility with older applications. As such, the possibility technically exists for new exploits to be found. It is highly unlikely, though.