That is what it looks like to me on my wife's computer:

1. Before the Feb2018 Cumulative Update even started to download, updates for Malicious Software and Defender Antivirus were shown as waiting to install.

2. Cumulative downloaded, has been on install 100% for at least thirty minutes.

3. The two updates in (1.) are still waiting.

That is why I suspect the updating system is stuck, and I don't know what to do about it. I am tempted to restart the computer, but I have no idea what damage, if any, that might cause. Ideas, suggestions, magic incantations are invited. Meanwhile, I am just going to leave the updater as it is; perhaps it will figure out what to do on its own, although I am doubtful, given the strange situation that exists.

I wonder how my wife's computer read this message: I just checked, and found her computer ready to restart to install the Cumulative, which it is doing as I write this. The other two updates are not even showing. I guess her computer felt threatened, and decided to take action....