The new Windows 10 Insider Preview build that Microsoft delivered last night was accompanied by a new cumulative update for the shipping version of Windows 10. This is perhaps not coincidental.

As you may know, Microsoft ships monthly cumulative updates for Windows 10 on Patch Tuesday. But this month’s release already happened last week, right on schedule. So what’s up with this second cumulative update?

Actually, these kinds of releases aren’t all that uncommon. As I noted recently in Updating in Windows 10 Version 1703? You Win Some, You Lose Some, the entire point of Windows as a Service (WaaS) is that Microsoft can update your PC anytime it wants.

Cumulative updates like the one we’re seeing this week (and last week’s Patch Tuesday release) are part of a broader series of “other” updates that fix bugs and/or security issues but do not add new features. (Microsoft ships more disruptive feature updates, like the Creators Update, once or twice a year. I feel that feature updates should be renamed to upgrades, but whatever.)

So this could be nothing. Or, as I’m now wondering, it could in fact be related to an interesting little note in Microsoft’s announcement about Windows 10 Insider Preview build 15063, which, as Brad noted, looks to be pretty damned close to RTM.

“The upgrade path from the Windows 10 Anniversary Update (Build 14393) to this Windows 10 Creators Update build is not yet live,” Microsoft’s Dona Sarkar wrote last night. “[It] will be live tomorrow morning.”

Obviously, the “upgrade path” could simply be an online lever that Microsoft can (virtually) pull. More likely, however, is that the currently shipped version of Windows 10—e.g., Windows 10 version 1607, or what Ms. Sarkar is calling build 14393—needs to be updated to allow for the upgrade to the Creators Update.

Whatever the reason, the cumulative update you’re seeing today—KB4015438—isn’t all that major compared to the normal monthly updates. And it appears to address two fairly unimportant issues. Curious that.