For those worried about "Access your data for all websites", this is an unavoidable problem with addon permission scopes. Put by the purported (likely?) author on a forum:

> IPvFoo author here. The problem is that there's no way to obtain the (hostname, ip) stream from Chrome/Firefox without requesting the "all websites" permission.

> In theory, browser vendors could define a narrowly-scoped permission that only reports (hostname, ip), or roll this functionality into the browser UI, but neither seems likely to happen.

> I made IPvFoo to promote IPv6 adoption, and wouldn't consider selling it for less than $10M USD. It probably won't ever be worth that much because it's an easily-cloned utility without a "moat", but it's more rational to set a price than refuse to sell under any circumstances.

The addon is open source, and if you insisted, could be built/installed manually. However, I trust it for now from here on AMO.

UPDATE: Thanks for confirming, Paul!