With insufficient configuration, it is possible that the browser's DNS requests will be sent to the ISP DNS server directly, and not sent through the VPN or Proxy. Thus, a malicious website will be able to find out the name of your real ISP, and the ISP will know your endpoint IP and which sites you visit.
DNS Leak Test shows which DNS servers your browser uses to resolve domain names. This test attempts to resolve 100 randomly generated domain names asynchronously, 50 with A record (IPv4-only) and 50 with both A and AAAA records (IPv4+IPv6).
Your IP Address
DNS Leak Test
|Your DNS Servers|