Here's a way to by bypass that- point the FF dev tools soley at the iframe, then use the scratchpad to run the alert. It will accept that and let you move past.

Here's a way to by bypass that- point the FF dev tools soley at the iframe, then use the scratchpad to run the alert. It will accept that and let you move past. I spent 20 minutes thinking I had something horribly wrong until I read this comment. (This works in FF 52.0a2)