Hi Dave,
I've just done a clean install of Windows 10 (latest edition) together with P3D V5.4 and PF3. During the cumulative update for PF3, my Windows Defender AV detected the following:-
Trojan:Script/Wacatac.B!ml
Details: This program is dangerous and executes commands from an attacker.
Affected items:
file: C\Users\kenne\AppData\Local\Microsoft\Windows\NetCashe\IE\F8M0CVAW\PF3_Cumulative_Updates_setup[1].zip.
The threat has been quarantined.
Brgds
Ken