From my testing using HMA VPN:
Opera 27.0 is also affected - It showed my ISP assigned IP address as well as the IP address the VPN assigned.
Internet Explorer 11 is not affected, probably because it does not support WebRTC.
The choice of VPN protocol also seems to matter. If I connect using OpenVPN, which is the default protocol most privacy VPN services use, this test reveals both my real and HMA assigned IP addresses.
However, if I connect using the PPTP protocol (as natively supported by Windows "Connect to a workplace"), this test only reveals the HMA assigned IP address on the three affected browsers.