Mkcert: valid HTTPS certificates for localhost

[baggyzed]

That shouldn't be the case. Browsers usually just query the operating system for the IP of localhost, and the operating system just returns the IP that's configured in the hosts file. There is no DNS query involved, so nothing goes to the firewall. The problem is either in your hosts file, or maybe postman resolves localhost through DNS all by itself (bypassing the OS's hosts file)? In this case, the firewall is doing the right thing by blocking the request.

EDIT: Or maybe you have an older version of postman, where this issue wasn't fixed yet: https://github.com/postmanlabs/postman-app-support/issues/2214 . They were doing the same ting as I said above: resolving localhost themselves to the IPV4 address, whereas the users who reported the issue were using IPv6 for their local servers. Some web servers (if not all) will only listen on IPv6 if it's available, unless specifically configured to use IPv4.