Hi, I was able to reproduce on IE8 and IE11.
Warning only appears if website is deployed on local network, and intranet features are enabled. By default they are disabled but prompt is displayed to enable it.
If intranet not enabled, no issue. If enabled, same warning on IE8, IE9 and IE11. The plugin must contact external website? Current production plugin works without warning.
Not a massive drama anyway, just annoying warning.