ERROR 403 when searching by author
Original: https://wordpress.org/support/topic/error-403-when-searching-by-author/
Searching by author makes 403 error on the site.
Possible reason: The problem was in the .htaccess file. With this part (which pretends to discourage brute force attacks by blocking author scans)
Solution: in .htaccess file remove next code if its exists:
RewriteEngine On
RewriteBase /
RewriteCond %{QUERY_STRING} (author=\d+) [NC]
RewriteRule .* – [F]