[withinrafael]

All the old builds of Windows 10 listed were presumably grabbed via public Unified Update Platform (UUP) infrastructure or the Ecosystem Engagement Access Program (EEAP), but I haven't confirmed yet. It's common knowledge in the Windows enthusiast community that builds (yes, even arm64 desktop Insider builds) can be pulled from Microsoft via these channels. It's not confidential, and not useful to share with anyone other than a build vault like Beta Archive.

Debugging symbols for most of those builds are available on symsrv.

The Windows Mobile Adaption kit (like the OEM Preinstallation Kits, OEM Adaptation Kits) is shared with a similarly sized audience, which used to include self-attested Microsoft Partners. Again, not confidential. Just gated stuff.

The Shared Source stuff is a slight unknown here because it's not clear what was in the ZIP. I presume this was a sampling of materials shared via the Shared Source Initiative (https://www.microsoft.com/en-us/sharedsource/), none of which includes high-value intellectual property, cryptographic code, third-party code, etc. It could still be damaging but Microsoft has clearly calculated the risk here; this stuff is shared with mere community MVPs.

So with all this knowledge, it's hard to digest the "omg more exploits coming" and "Microsoft lost 32TB of private IP" angles in The Register write up. I don't think there's a story here, frankly.