Windows 7 Update appears to be compromised?

Same here.  Looks to be exact same pieces as well.  On mine, last update I went through was 9/28 when everything was reported as "up to date", which had installed Definition Update for Windows Defender KB915597 (Definition 1.207.973.0)

Today I saw two updates available - Definition Update for Windows Defender KB915597 (Definition 1.207.1296.0) and this Language Pack.  I disabled the language pack and marked it "hidden".

I also ran SuperAntiSpyware and MalwareBytes anti-malware with databases updated this morning and they found nothing.  I'll run Windows Defender and FortiClient next.

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Download size: 4.3 MB

You may need to restart your computer for this update to take effect.

Update type: Important

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More information: 

https://hckSLpGtvi.PguhWDz.fuVOl.gov

https://jNt.JFnFA.Jigf.xnzMQAFnZ.edu

Help and Support: 

https://IIKaR.ktBDARxd.plepVV.PGetGeG.lfIYQIHCN.mil

People can reasonably be concerned and mistrust their computers until they get a clear answer.

Completely agree and they should. Something like this is extremely concerning. Especially with something that just doesn't look quite right. Something such as Windows Update getting compromised is highly concerning or any indication that it potentially could be.

That's the flame malware I refer to that got on systems with usb flash drives.  It wasn't trivial at all to compromise the system and since then the manner in which they tricked the systems (a TS server that generated bogus Microsoft CA certs) has been removed and there's been a metric boatload of CA /root cert/ WU hardening done in the meantime so that the manner in which that attack occurred then can't be replicated now.

https://social.technet.microsoft.com/Forums/office/en-US/18eeca65-21e1-42df-b882-8c1b099f1a7f/updates-needing-files-2-downloaded-133254-mb-of-133305-mb?forum=winserverwsus

Note that thread.  See the same pattern of the funky server name - the rr1winwusfs04 referred to?  Back in August there was a similar issue where a  "test update for supersedence" was released.  Again my gut is still telling me this is not nefarious.

People can reasonably be concerned and mistrust their computers until they get a clear answer.

Agreed.

MS are obliged to say something.

Could you please do the following:

Please zip-up the contents of the folder:

C:\Windows\SoftwareDistribution

And send the zip to secure@microsoft.com, referencing this thread so that Microsoft can triage what's going on here.