A Windows 10 feature, Wi-Fi Sense, smells like a security risk: it shares Wi-Fi passwords with the user’s contacts.
Those contacts include their Outlook.com (nee Hotmail) contacts, Skype contacts and, with an opt-in, their Facebook friends.
But don’t worry!
Wi-Fi Sense doesn’t reveal the plaintext password.
Unless, of course, something goes wrong….
In an attempt to address the security hole it has created, Microsoft offers a kludge of a workaround: you must add _optout to the SSID (the name of your network) to prevent it from working with Wi-Fi Sense.
(So if you want to opt out of Google Maps and Wi-Fi Sense at the same time, you must change your SSID of, say, myhouse to myhouse_optout_nomap. …)