server {

   ...

   # ==========
   # HTTP security Headers
   # ==========

   # HSTS (ngx_http_headers_module is required) (15768000 seconds = 6 months)
   #
   add_header Strict-Transport-Security "max-age=31536000" always;

   add_header X-Frame-Options "SAMEORIGIN" always;
   add_header X-XSS-Protection "1; mode=block" always;
   add_header X-Content-Type-Options nosniff always;

   add_header Referrer-Policy "strict-origin";

   # - Geteiltes Dokument öffnen
   #
   #      # Add Etherpad-Lite host to frame-src, so frame-src becomes:
   #      #
   #      #    #frame-src 'self' https://<etherpad-lite-host> https://www.youtube.com ;
   #      #
   #      #    i.e. etherpad-litehost = epad-01.oopen.de
   #      #
   #      frame-src 'self' https://epad-01.oopen.de https://www.youtube.com ;
   #
   #
   # - YouTube-Video teilen
   #
   #      # Add https://www.youtube.com to script-src, so script-src becomes:
   #      #
   #      script-src 'self' 'unsafe-inline' https://www.youtube.com ;
   #
   #      # Add https://www.youtube.com to frame-src, so frame-src becomes:
   #      #
   #      frame-src 'self' https://meet-ep-pee7eiji-xein9aiy.oopen.de https://www.youtube.com ;
   #
   #      # Add https://img.youtube.com to img-src, so img-src becomes:
   #      img-src 'self' https://img.youtube.com
   #
   #
   # - Hintergrundschärfe aktivieren:
   #
   #       # Add https://storage.googleapis.com to connect-src, so connect source becomes:
   #       #
   #       connect-src 'self' https://storage.googleapis.com;
   #
   #       # Add blob: to script-src, so script-src becomes:
   #       script-src 'self' 'unsafe-inline' https://www.youtube.com blob:
   #
   # Note!
   #   Other directives (like worker-src, or child-src, or..) are falling back to 'default-src'.
   #
   add_header Content-Security-Policy "default-src 'none'; script-src 'self' 'unsafe-inline' https://www.youtube.com ; img-src 'self' https://img.youtube.com ; style-src 'self' 'unsafe-inline' ; font-src 'self'; frame-src 'self' https://epad-01.oopen.de https://www.youtube.com ; object-src 'none'; frame-ancestors 'none'; form-action 'self'; base-uri 'self'; connect-src 'self' https://storage.googleapis.com ; media-src 'self'";

   # Etwas allgemeiner dafür auch etws unsicherer formuliert:
   #
   #add_header Content-Security-Policy "block-all-mixed-content ; default-src 'none'; script-src 'self' 'unsafe-inline' https: blob: ; img-src 'self' https: ; style-src 'self' 'unsafe-inline' ; font-src 'self'; frame-src 'self' https: ; object-src 'none'; frame-ancestors 'none'; form-action 'self'; base-uri 'self'; connect-src 'self' https: ; media-src 'self'";


   add_header Permissions-Policy "geolocation=();midi=();notifications=();push=();sync-xhr=();microphone=();camera=();magnetometer=();gyroscope=();speaker=(self);vibrate=();fullscreen=(self);payment=();";

   ..
}