In the past, we offered users a way to list and browse the packages available on the pkg mirror, e.g., at http://pkg.freebsd.org/FreeBSD:12:amd64/quarterly/All/.
Due to the cost of handling such requests, the site now returns 403 instead.
We should either present users with a static website explaining the change or at least document what happened in, e.g., FAQ.
(In reply to Mateusz Piotrowski from comment #0)
Yes and I think it would be a good idea to create an index.html in those directories, and instruct people that the same information can be retrieved by downloading and parsing https://pkg.freebsd.org/FreeBSD:12:amd64/quarterly/packagesite.txz
I believe this need to slightly modify the pkg mirror scripts to put that static page. It may take a while to research how to do so (or asking one knows) but it is worthwhile to do so.