Microsoft Confirms Windows 10 Cumulative Update KB3135173 Resets Default Apps

Earlier this month, we reported that Windows 10 cumulative update KB3135173 reset the default apps on a number of PCs running Microsoft’s new operating system, although its default behavior wasn’t clearly supposed to lead to such changes.



At that point, many accused Microsoft of using this cumulative update as a tactic to set its own apps as default on Windows 10, especially because many were replacing programs such as Edge browser with third-party solutions.
“We had to do this” But in a recent statement, Microsoft says that it doesn’t change the default apps on Windows 10 with this update because it wants its programs to be used once again, but only due to the fact that some third-party tools were spotted messing with this system in ways that could affect OS performance.
“We’ve seen behavior by some apps that have set themselves as default in unsupported ways by deleting or corrupting registry settings. Details on supported methods for apps to register file associations can be found on MSDN here,” Microsoft explains.
“Update KB3135173 for Windows addresses the problem and resets application defaults to the initial Windows settings when registry settings are deleted or corrupted. We have worked with some of these app providers so the apps no longer exhibit this behavior in their latest versions. If a user proactively changes their default app settings using the supported method, the registry won’t be corrupted and those user settings are retained.”
So there you go. Microsoft doesn’t change default apps because it wants to, but because it has to, as these third-party programs are changing this behavior without you specifically asking them to do it.
As usual, if you want to configure your own default apps, you can click Start > Settings > System > Default apps, and in each section pick the program that you intend to use as default.