Hi Olyphant,
Lua AddOns themselves can't really contain virus's, it's just text and maybe some graphics. I would say it's more likely a bad ad triggered the message. We will certainly audit our ads we even subscribe to a service that is supposed to scan for bad ads they try and sneak in. If you had any other websites open in your browser with ads at the time it could have come from there too.
Very sorry to hear this happened to you.
