Security update 2019-006 10.13.6 does not install

Trash that installer and try it from here, this is off a different server.

Download Security Update 2019-006 (High Sierra)

If that doesn't work try installing in Safe Mode:

Use safe mode to isolate issues with your Mac - Apple Support

How do I "trash" the installer? This update gets stuck trying to turn off the computer during the update process. Nor can I manually shut the computer down without the shutdown hanging.

App Store continues to remind me that I need to "restart" my computer to finish this update, but as noted above, this does not work...

I had trouble with this update also, and noted it in another post.

The update seemed to complete with a few automatic restarts and this brought me to a login screen.

To my surprise, my keyboard was dead ! (wired extended apple keyboard.).

Naturally any keyboard commands could not get me out of this situation.

Finally I tried holding down the start button on the back of my iMac (mid 2017) which seemed to shut it down OK.

I unplugged it from the wall (SMC) restart for a few minutes. Then plugged it back in.

Then I hit the start button again and did the PRAM routine which actually didn’t help the first time.

Doing this process 2 more times finally brought me to the login screen again and I was so happy to see my keyboard responding again. 

Phew, scary for a while there.

Next time, for security updates I plan to do it in safe mode, if I can. 

Yes, these las few security updates do seem troublesome.

I wonder what is really going on.

.

This has been the case with every other 10.13.6 security update, no exaggeration. Why are they made available if they don't work? It leads to premature installation.

Press these three keys together: Option, Command, and Esc (Escape). This is similar to pressing Control-Alt-Delete on a PC.

Then Force Quit the Installer.

This (updating in Safe Mode) worked for me in completing the download, which got rid of the can't use Safari while updating error message. Two problems solved.

Great to hear, thanks for the report! :)

wow this update security ruin my mac pro 5.1 system with nvidia drivers and i was unable to restore from yesterday time machine good job apple ....!!!