After installation of KB4056892 boot failure, after roll-back error 0x800f0845

The vulnerability only becomes an issue if unauthorized users are able to run code on your system.  How they could do so is another matter, though it could be in numerous cunning ways.  The issue is that this can take advantage of a weakness in practically every CPU ever built - with the exception of Intel itaniums, and there is no real way of flagging that there has been a compromise.  

Nope, those vulnerabilities can be exploited through a plain Javascript.

> We should also take into account that WIN10 will happily run on our 10-15 year old hardware, which is a fantastic compatibility feature you should give MS some kudos for.  Its certainly given a couple of bits of kit, including an ancient Dell laptop, around here a new lease on life. 

Nope we shouldn't, GNU/Linux runs perfectly on bunch of hw from ancient boxes and odd CPU architectures to most modern desktops and supercomputers. So why Windows shouldn't work on old devices?

> Come to think of it I have bits of hardware here that used to work just fine, scanners and printers, yet the new OS drivers just stopped being made available, which pretty much forces you to buy new equipment, or retain win98/xp boxes simply to connect a favourite scanner.. so keep this in perspective, you can buy a complete system for what my old scanner cost. 

Or you can put smallish GNU/Linux distro just for the purposes of still having working drivers, and at the same time gonna have all those Meltdown/Spectre patches, etc.

I will try this.  Wouldn't it be good if MS would run this patch first?  Seems logical instead of force updating to make the system usable unless someone like you lets us know.  I hope this works and I will try it out as soon as I know I have a few hours to test.  Took quite some time to get my system back from before and no it did no roll back the update.  If I had not had a system restore that I manually created (since MS also turned off those too) then I would have had to do a windows repair that BTW can not be run from the install disk because MS fixed that as well.

Risk?  The only risk as you say is if someone runs code that should not be run on a system that has been doing fine for a decade.  So yes I would rather take a risk than have my system forcibly disabled by the OS.  No that is not going over board that is just a fact.  If someone has a system that is vulnerable then MS simple makes it so it does not work.  The same as if you had a virus attack.  So no it is not bashing it is fact.  Rather than disable the system intentionally then would not have it been better to run a check on the system and pop up one of those annoying alerts that Windows 10 forces on us anyhow?  Your logic is flawed by saying we should run an update that prevents the system from being used rather than risking that an unlikely attack happen directly at the location.

I'm certainly not a huge MS fan at the moment, they make me feel like a beta tester at times, but can we not go too overboard on the vendor bashing.   

For those who dont know, Spectre/Meltdown is a vulnerability (not a virus), and rather a major one, so i can see why they were falling over each other trying to get patches out there.   Even Intel released a ROM update prematurely, which was subsequently retracted, god knows how many workstations were patched with that.

The vulnerability only becomes an issue if unauthorized users are able to run code on your system.  How they could do so is another matter, though it could be in numerous cunning ways.  The issue is that this can take advantage of a weakness in practically every CPU ever built - with the exception of Intel itaniums, and there is no real way of flagging that there has been a compromise.  

Its also referred to as side channel, where system area CPU computation can bleed into the user area, which effectively means if you wear a hoody, and can force and read those overflows, then there is a good chance of eventually capturing all sorts of privileged information that is executing.  

According to MS, the AMD problem was caused by the specifications on the older AMDs chips not being reported accurately, I don't know whether that is correct or corporate speak for 'we stuffed up, and will not admit it'. 

So yes these are annoying patch workarounds, as is the complete invisibility of MS support, but then would you rather live with the risk of no patches? 

BTW -  I have a completely unpatched VISTA32 machine system happily humming away after 11 years, simply because its only purpose in life is to run Windows Media Centre - and it will never touch the internet, or a proxy, thats the only box i would not bother patching. 

We should also take into account that WIN10 will happily run on our 10-15 year old hardware, which is a fantastic compatibility feature you should give MS some kudos for.  Its certainly given a couple of bits of kit, including an ancient Dell laptop, around here a new lease on life. 

Come to think of it I have bits of hardware here that used to work just fine, scanners and printers, yet the new OS drivers just stopped being made available, which pretty much forces you to buy new equipment, or retain win98/xp boxes simply to connect a favourite scanner.. so keep this in perspective, you can buy a complete system for what my old scanner cost.

Define a virus then think about MS liability.  Even after knowing what this does they keep forcing it on people.  A virus intentionally harms your system then this is a virus and needs blocked.