For more information about the remaining security vulnerabilities released on June Patch Tuesday, visit Microsoft's Security Update Guide.
Significant numbers of users still run Windows XP and Windows 8, the two unsupported desktop-grade versions that Microsoft updated.
Windows XP use remains significant: there were millions of people running the operating system as late as previous year.
Topping the priority list should be zero-day vulnerabilities CVE-2017-8543 and CVE-2017-8464, both of which Microsoft said are being exploited in the wild. But the company sought to emphasize that updates for older systems will not be routine. Now it has released another security update for Windows XP, this time due to the "heightened risk of exploitation" by copycats. Independent discovery for some of the fixed vulnerabilities occurred before the Shadow Brokers leak, indicating researchers and malware authors are still interested in finding problems in legacy versions of Microsoft products.
In a press statement released by Microsoft earlier today, it has underscored the importance of this update in the face of an imminent threat.
Tuesday's issuance of down-level patches is only the latest in a series of unusual events involving Microsoft's once-predictable security update regimen. Peter Bright, from technology site Ars Technica, said: "patching is the wrong decision: it sends a clear message to recalcitrant corporations that they can stick with Windows XP, insecure as it is, because if anything too serious is found, Microsoft will update it anyway ..."
However, there is one more reason why Microsoft is so careful. It's important to note that all Windows users are getting these security updates, including those who are on currently-supported Windows software.