Quote from Richard Cournoyer on February 16, 2020, 3:04 am

I have had a problem with the ST Link (Blue Pill) APP stating that the HEX firmware file is Corrupt or Empty.  The problem exists because Windows is saving the link/file as a HTLM (or similar) file format which is why it arrears Corrupt in the ST Link APP.  

Here is what you need to do to fix the problem:

1. Go to GitHub page that has the Firmware files.
2. Click on the HEX file
3. On the HEX file page, find the RAW button (HInt: It's in the upper right corner of the page) and Right Click and save as on THAT (RAW) File Type.
4. Continue with the Firmware update using the ST Link APP/Tool