The default application proxy returned by QNetworkProxy::applicationProxy();
used to be of type QNetworkProxy::NoProxy. However, it appears that somewhere between 5.7 and 5.9.1 this has changed.
It's now returning QNetworkProxy::HttpProxy.
Given this code:
On 5.7 I get: 0 and 2 in the output.
On 5.9.1 I get 0 and 3 in the output.
This caused some of our connections to report "Host not found" because we had never explicitly set the proxy on the network access manager.