Trojan in winscp400setup.exe

Today's log from up-to-date AVAST Antivirus:

2007-05-03 12:17:18 SYSTEM 1032 Sign of "Win32:Trojan-gen. {Other}" has been found in "https://winscp.net/download/winscp400setup.exe/download" file.

Same happens from other SF mirrors, WinSCP 3.8.2 seems OK.

Could you please explain?

I believe that it is false report. But please try to verify checksum of a file you've downloaded.
Issue 530 – WinSCP detected as trojan/virus