Pretty sure it’s a false positive Kaspersky has done the same thing in the past, apparently it has something to do with how the reporter writes its logs (and other possible reason noted below):
While I disagree that antivirus is unnecessary, they are definitely not infallible and I would be inclined to trust most of what Steam lets on their distribution servers…
Edit 2 - Ignasis also commented on a similar issue some time back:
Kaspersky has done the same thing in the past, apparently it has something to do with how the reporter writes its logs (and other possible reason noted below):