My guess is that is from within a WebLobby window using the Flash client? The browser that WebLobby uses emulated Internet Explorer 8 by default. That's why you are getting the warnings.
There is one trick you can try and that is to set the browser emulation by creating a registry entry.
Run RegEdit and go to the following key
look to see if there is a key there called FEATURE_BROWSER_EMULATION. If the key does not exist create the key.
Now go into that key
Inside that key create a new DWord entry called MainLobby.exe
Once created edit the entry and set its value to 11000
Now the browser will emulate Internet Explorer 11