Resilio Sync version: 2.5.9
Windows 10 Pro
What happened: I uninstalled Sync so I can reinstall it as a service. I checked "Delete settings" during the uninstall. It proceeded to delete everything on C: drive.
Except the files currently locked by Windows, all of C:\Users, C:\Program Files, C:\Program Files (x86), C:\Windows, and more are gone.
How do I know it's the culprit? Because I watched Resilio Sync.exe in Task Manager consuming 100% of disk activity on my administrator username, and my available disk space on C: increasing by the GB's in seconds.
Chrome still works because it was open when the mass deletion happened. I don't think my computer can reboot now. Please don't test this bug without a full backup stored somewhere else.