Over its short lifetime, Windows 10 has already received a number of cumulative updates that combine security fixes with some number of non-security bug fixes and perhaps even the occasional new feature. To be honest, we're not entirely sure what the cumulative updates contain, and there's a simple reason for that: while security updates do receive official documentation and enumeration, the non-security stuff is not described by Microsoft at all. When asked about this last month, Microsoft affirmed that it has no plans to tell anyone what's in the updates.

This is frustrating. If an organization is holding back on deploying Windows 10 because of bugs it has experienced, it would be useful to know if those bugs have been addressed. Even when Windows 10 has been deployed, it's helpful to know if a given build is supposed to fix a particular bug, as it can aid diagnosis of issues and make clear what's supposed to be happening, even if something isn't working correctly. Any user-visible functional changes make this even more important; if the operating system is going to change, people should be given some idea of what to expect.

At a time that Microsoft should be striving to build confidence in "Windows as a service" and its new update and release model, its peculiar reluctance to explain what goes into each update seems more likely to drive IT departments into using the infrequently updated Long Term Servicing Branch instead of the mainline Windows release. Microsoft's guidance is that LTSB should be used only on those mission critical systems that absolutely cannot tolerate anything more than security fixes, but if the company is going to keep people in the dark about what they're installing with each update, plumping for LTSB may well be the rational choice for the concerned administrator.

During a visit to Microsoft's campus a couple of weeks ago, we were told that the company might try to provide a little more information for IT departments—though we feel it should be made available to all—but still did not commit to providing any kind of serious release notes. And the official line is still that there are no plans to provide release notes.

This strange decision is made even more surprising, because Microsoft does actually create release notes for some, if not all, builds of the operating system. From time to time, this information leaks. Veteran Russian leaker WZor published on Monday the release notes to Windows 10 build 10537 and the notes for build 10540. This isn't the first set of release notes published this way, either. The release notes for the launch-day patches were similarly leaked.

The leaked documents do all the kinds of things that release notes should do. They describe new features, both user-facing (such as a new look to the context menu that you get when you right click the Start button) and administrative (a new default that locks down the Edge browser more thoroughly, along with a way of unlocking it should it be necessary). They describe the bug fixes that are included and the known bugs that still exist.

It's hard to know how complete these notes are. The documents describe the list of bug fixes as "a list of some recently reported bugs, which are fixed in this build," implying that other recently reported bugs, and any older bugs, aren't included, even if they have been fixed. The description also says that "many of the fixes" have also been delivered to Windows 10 RTM as part of the cumulative updates. We just don't know which ones.

Obviously, for public distribution Microsoft might want to tidy these documents up somewhat. References to internal bug IDs don't really need to be made public, for example, given that the bug tracking system itself isn't public. The formatting could be improved, and some of the workarounds would need further elaboration to make them appropriate to a wider range of users.

But fundamentally, Microsoft is doing the work and creating the documentation that its Windows updates should include. The company does know what its updates are doing. So why won't it tell us?