I can't guess what malware did this to my brother and client PCs but I'm running into systems that we can't repair the boot. Even with other tools like EasyBCD and such. This is not limited to Windows 10 but 7, 8, 8.1, XP and you get the idea.
What this means is nothing has fundamentally changed. We must maintain backups and test the recovery options.
My last encounter (I see this stuff weekly) was a Dell with a blinking cursor. The Dell diags (press D on power up) seems to tell me it was not hardware. So I used the Windows 10 Recovery with full restore files and the machine came back fine. Yes, the user files are gone but that was on backups so they lost nothing.
After Windows 10 decided it would not start any more I thought, No problem, I made a recovery disc and tested it a few times to make sure it worked. So when it would not start I put in the USB recovery disc I made and first tried the startup repair and it said it could not be fixed. So I went to the command prompt and put in the commands that should repair the MBR and Bootrec, All the fix boot stuff and no go. So I thought I better do a reset and it went through an hour recovering my OS "NOT" at the end it said it could not start the OS even though it did boot into the first windows environment. I tried everything the Recovery disk offered and a bunch of("every") Command in c prompt that had any hope of fixing it. I could see everything there though with a live Linux boot but no hope of repair. I'm now back with 7 on both machines with linux mint as a back up OS. Windows 10 advertised this as bullet proof with the new recovery environment. Seems more like a half baked fruit cake now !