Unexpected popup from NetworkManager

Ever since I upgraded to Gnome 3.24 I’ve been getting some weird popup-like windows. It looks like when you access a ftp directory with a webbrowser. It says something like: Accesspoint login. Gnome nm check network connection and a link to a text file. I’m not connected to any weird hotspot network. Normal home WiFi router. As soon as I click on the supposed link to the text file the window disappears (crashes?). Is this something new in gnome 3.24? Did I accidentally enable it? Or is it something else?