Hey Guys, I tried upgrading my mac to High Sierra and I am getting this error. Any suggestions on what may be the cause? I am running Sierra right now.

I have original drive but still have issue.It's apparently related to some third-party drives. If you still have the original drive then you can install to that, then put your third-party one back in and install again (the firmware is already updated so it'll work the second time).
I "fixed" it somehow and got High Sierra working last night.same error here. mid-2010 15" MBP with Crucial SSD
If you can, try to unplug all external (USB) devices. That appears to have helped in my case.Hey Guys, I tried upgrading my mac to High Sierra and I am getting this error. Any suggestions on what may be the cause? I am running Sierra right now.
Hey Guys, I tried upgrading my mac to High Sierra and I am getting this error. Any suggestions on what may be the cause? I am running Sierra right now.
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Not even in safe mode the installation finished, not errors with disk utility or via terminal (not SSD). All seem to work ok except verification of firmware during installation. I give up for now since my next shot is clean install
i have the same exact problem from beta versions of high sierra since the official on a late 2009 iMac. Cannot install high sierra. First time all these years i face that
I ran into the same issue last night on my genuine MacBook 12" 2016. There was a problem that might have triggered this error. My guess is I had a firmware password set and didn't disable it prior to installation, thus EFI update couldn't work. High Sierra performs an EFI update to enable APFS
I did a clean install anyway so I formatted my SSD to HFS+ journaled. Then ran High Sierra installer from USB-drive. The first attempt failed and produced the same error the OP had above.
This was my approach.
1. Make sure you have firmware password disabled.
2. Use MacOS Sierra 10.12.x (or earlier?) recovery/install USB-drive.
3. Boot from Sierra Recovery (hold Option-Key after reboot)
4. Open Disk Utility, format entire SSD to HFS journaled, run first aid. Shutdown Mac.
5. Reset NVRAM and SMC
6. Install High Sierra from USB-drive again. If you get the error again (I did), abort and shutdown.
7. Boot from Recovery on your SSD. High Sierra should have installed it. (Hold Command-R after reboot)
8. Open Disk Utility and format entire SSD again to HFS+ journaled.
9. Reboot. Your Mac is bricked now.
10. Boot from Sierra 10.12.x Recovery USB drive
11. Open Disk Utility and NOW you should see an EFI partition which is unmounted (was in my case).
12. Mount the EFI partition. The EFI partition will disappear. Format SSD again to HFS journaled
13. Install High Sierra from USB-drive. This time it should work.
What a hilarious nightmare... Thanks Apple!