Lots of Windows users found a watermark on their desktop saying “SecureBoot isn’t configured correctly” along with the version and build number of Windows 8.1.
This is a bug fixed by Microsoft.
To remove the “SecureBoot isn’t configured correctly” message from your desktop, you would need to download and install the patch from Microsoft below:
After installing the patch, re-start your PC and the watermark should be gone.
For more info. Visit the Microsoft article 2902864