Show this in the extension only to that user.
You could use the Extension PubSub Whisper Topic for this.
or use either kind of pubsub (channel or whisper) to relay the “winners” list then the winners instance of the Extension makes the HTTP Call to fetch prize data.
Probably what I would do. But I’d only show the winners the claim button
Basically: whispers are a no go.
Even more so when you intend to sent “reptitive”/similar message to every user that you are gonna whisper.
And it just makes sense to keep all the extension stuff inside the extension. As then users are not opening other windows for the same data.
Reply to the user in the same place they started the interaction.