GSC Indexing Problem

You would need to disable the policy (Firewall Policies > Protect against username enumeration > Through the author archives) if you want bots to access it.
Alternatively, you could whitelist the IP address(es) using the “.htninja” script: https://blog.nintechnet.com/ninjafirewall-wp-edition-the-htninja-configuration-file/?#allow_block

Thanks for your response. What should I whitelist exactly, which IPs?

I solved the problem anyways with a simple method. For people who use NGINX, add this block to your sites’s configuration which block user enumeration scans from the user archives page and disable it from the ninja firewall:

location ~* {
if ( $query_string ~ "author=([0-9]*)" ) { return 403; }
}

• This reply was modified 1 year ago by Ivan Salloum.

Do you mean you want to block the request with a 403 code, even when it is Google, instead of the 302 redirection code returned by the firewall?
I thought you wanted to allow only Google to access it.

No, that’s not my point. When enumerating users, you can use ?author=1 and ?author=2. When I let Ninja Firewall handle this, it blocks these requests but it blocks also requests made to the author archive page when visiting ivansalloum.com/ivansalloum and this doesn’t make sense. To prevent enumerating users, we just need to block such requests like ?author=1 and not when people visit the author’s page that has posts listed written by him/her. That’s why I used the NGINX block to prevent user enumeration attacks and disabled it from Ninja Firewall for user archives.