CloudCity

I also have that "Youtube Best Video Downloader 2," and after disabling it, no more "worldnaturenet.xyz" nuisance alert from MWB. I will be removing that YouTube downloader permanently from my Firefox add-ons. Thank you, all.

I have the latest Firefox, and it does it there too, so it's not just a Chrome issue, although I have to say that it doesn't happen every 5 seconds in Firefox. The message only appears when first starting Firefox, and whenever a new tab/window opens in Firefox during the same session.