I have a attached a screen capture of what I see on my settings for my Update and security. I just noticed this recently and while it says "Pending Install" it has been there for several days but has not automatically installed. My question is should I click on Install Now?Install update.JPG
It is Windows 10, so chances are it will decide to install itself at some point. However, I would recommend making an image backup before installing it, as it is possible that it might cause issues including but not limited to significantly slowing down your system. I would also try the inSpectre tool to check on what patches, if any, are already installed and which ones you may still need.
I have downloaded and executed the InSpectre tool with the result shown on the attached screen capture. I will wait for Windows 10 to auto install it and I have an Image BU.