As our existing code signing certificate is expiring on 2020-01-23, we have renewed it.
Though we didn't know that Microsoft Defender SmartScreen will consider the renewed certificate as a new one and will trigger a warning:
"Windows Defender SmartScreen prevented an unrecognized app from starting"
The warning will be displayed until the certificate builds a reputation. Criteria for that are not known. See also: https://security.stackexchange.com/q/222140/43677
Until that reputation issue is resolved, we plan to release a new version of WinSCP stable branch (5.15) with the old certificate. The new certificate will be used only for the development branch (5.16) for now.
Though by installing a version that uses the new certificate you are helping us building the reputation of the new certificate. So please consider that.
To dismiss the warning, click "More Info" and then "Run anyway".
If you want, you can verify an integrity of the installer: