WordPress website shows content incorrectly: all icons are shown as a square

Symptoms

• WordPress website example.com or its Admin Dashboard shows content incorrectly - all icons are shown as a square:
  

• The following error can be found in Developer Tool of a Web Browser:

  Redirect has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'https://example.com' is therefore not allowed access.

• There is the directive in Plesk > Domains > example.com > Apache & nginx Settings > Additional nginx directives:

  #location ~ .(ttf|ttc|otf|eot|woff|woff2|font.css)$ {
  #add_header Access-Control-Allow-Origin "*";
  #}

  Note: This directive can be completely absent.

Cause

Incorrect nginx directive.

Resolution

1. Go to Plesk > Domains > example.com > Apache & nginx Settings > Additional nginx directives

2. Edit existing directive it should be like:

   location ~ .(ttf|ttc|otf|eot|woff|woff2|font.css)$ {
   add_header Access-Control-Allow-Origin "*";
   }