Windscribe does not have a "Killswitch', we have something better.
We have the Windscribe Firewall which is built into our Windows and Mac applications. It blocks all connectivity outside of the tunnel to ensure there is zero chance of any kind of leak, including but not limited to DNS leaks, IPv6 leaks, WebRTC leaks, etc.
A firewall is a superior solution to a "kill switch, as the "kill switch" is a snake oil feature and offers absolutely zero protection because it's a reactive measure. Between your VPN disconnecting and the program detecting that it did, packets can leave your computer over the default gateway (your ISP). A firewall blocks ALL connectivity outside of the tunnel. If the VPN connection drops, there is nothing that needs to be done, and not a single packet can leave the machine, since the firewall will not allow it. In geek terms it fails closed.
Learn more about the each of the Firewall modes here: https://windscribe.com/support/article/28/firewall-modes