The only way I know about the patch is Googles action but without a Fortnite account I don't know if Epic made any attempt to alert customers. Past experience with them suggests it's unlikely though and 90 days hoping users update before being exploited or warned is wrong.
It's very believable Epic would have left users with a vulnerable installer in place for a long time, certain that hackers would be looking at the installer of such a popular game, find the same issues and potentially bypass or block any later automatic update.