What's Windows 10 patch KB 3211320? Microsoft doesn't seem to know

In Microsoft's documentation, the new patch is described as both a servicing stack update and a critical security patch for Edge

What's Windows 10 patch KB 3211320? Microsoft doesn't seem to know
flickr/Robbie Biller

Last night Microsoft pushed out a patch for folks running the latest release of Windows 10 (version 1607). Unless you’ve taken steps to block updates, your PC probably installed it overnight. But there’s a problem: Nobody can say for sure what the patch does. There’s no documentation – or more accurately, there’s a surfeit of documentation, with at least two credible, conflicting descriptions of KB 3211320.

It’s likely that KB 3211320 is a servicing stack update – a new version of the software that handles Windows patches. But there’s also a credible description in Microsoft’s own posts that says KB 3211320 is a critical patch for Microsoft Edge, identified as MS17-001.

Yes, Gildna, new KB 3211320 is both a floor wax and a dessert topping!

The explanation I find most credible can be found in the Microsoft Update Catalog. Look up KB 3211320, then click on the link for the version of the patch that pertains to you to see the usual Update Details. Click on the tab marked Package Details (see screenshot) and the patch is clearly marked as superseding both KB 3199209 and KB 3199986. Those are the Windows 10 1607 servicing stack updates released on Oct. 18 and Oct. 27, respectively.

kb3211320 supersedence InfoWorld

You may recall that we had this same “Oh golly, what update did I install?” problem with KB 3199209. Microsoft has a history of pushing Win10 servicing stack updates without any warning and only a dribble of recognition long after the fact.

Poster Enthousiast on My Digital Life pulled the patch apart and independently confirmed its components.

Of course, as of this writing there’s no KB article for KB 3211320. You’re expected to install it because, you know, Microsoft.

Paradoxically, Microsoft also lists KB 3211320 as a Critical update for Microsoft Edge running on Windows 10 1607, as part of security bulletin MS17-001. It’s an Important / Elevation of Privilege bug that, according to the documentation, requires a restart. As many of you can attest, the KB 3211320 we got last night doesn’t require a restart.

As best I can tell, that security bulletin entry is wrong. It’s spawned a wave of fake news, saying that KB 3211320 is a security patch for Edge -- not true. Sad. Never mind that’s exactly what Microsoft’s own documentation says.

I haven’t even touched my pudding and I’m ready for more.

The discussion continues on AskWoody.com.

Thanks to ch100 on AskWoody and Enthousiast on MDL.

Copyright © 2017 IDG Communications, Inc.

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