Microsoft started fixing issues with Meltdown and Spectre updates last week where the first patches were issued to Windows 7 and Windows 8.1 computers, also, the rollout continued in the last few days with more updates aimed at Windows 10.

Today, the company published simply a new cumulative update for Windows 10 Fall Creators Update (KB4073291), but also updates for Windows 10 original version and Windows 10 version 1511 (November Update) - KB4075199 and KB4075200, respectively. Both are available comprising of cumulative updates and "address issues where some customer with AMD devices get into an unbootable state."

Additionally, KB4075200 also includes a fix for the bug causing a section of the system to no log off correctly, leading to repeated queries for user credentials. This reportedly happens only on Windows 10 version 1511 along with the update is shipped exclusively to Windows 10 Enterprise and Windows 10 Education, which means that Home and Pro won't be capable to install it.
"Two known issues, one impacting antivirus protection"

One can find two known issues in both cumulative updates, and Microsoft has also included workarounds to verify they install correctly.

One of the several bugs concerns incompatibility issues with antivirus solutions, a problem that first appeared as the company published Meltdown and Spectre security updates. Microsoft says that only machines running antivirus with the ALLOW REGKEY will acquire the cumulative updates, and the company recommends to contact the vendor and add the following key:
Key="HKEY_LOCAL_MACHINE"Subkey="SOFTWARE\Microsoft\Windows\CurrentVersion\QualityCompat"
Value Name="cadca5fe-87d3-4b96-b7fb-a231484277cc"
Type="REG_DWORD"
Data="0x00000000"

You'll discover no failed installs reported so far and given that these updates bring fixes for issues on AMD systems, clients are recommended to install them as soon as possible.

At this point, Microsoft has addressed the boot failures as well BSODs on all supported Windows versions, which means that all Windows computers should right now be rrn a position to recover following the botched Meltdown and Spectre update fiasco.