Set DefaultUpdatesPeriod to 0.
https://winscp.net/eng/docs/administration
Note that this will affect only users that did not start WinSCP yet.

Hello ,
I did installation through set up wizard on windows 2009 server and we publish the icon on citrix server.
I have disabled the update through the preference, but it only stops prompting for the current user. ( example, if 300 users are configured in AD like if one time user CLOSE the popup screen(see attached) they dont see that screen again)
But i dont want rest of the other users 299 to be affected.
Kindly help how to disable the pop up for end users.

Thanks in Advance!