Examples of Security Headers

Apache in .htaccess or httpd:
Header set X-Xss-Protection "1; mode=block"
Header always set Strict-Transport-Security "max-age=63072000; includeSubDomains"
Header set X-Content-Type-Options nosniff
Header set Referrer-Policy same-origin
Header set X-Frame-Options SAMEORIGIN

# and add customer specific:

Header always set Content-Security-Policy "default-src 'self'; base-uri 'none'; font-src 'self' data: https://example.com; frame-ancestors 'self' https://example.com; img-src 'self' data:; object-src 'none'; script-src 'self' unsafe-inline' 'unsafe-eval'; style-src 'self' 'unsafe-inline';"

Header set Permissions-Policy geolocation=()

Nginx:
add_header X-Xss-Protection "1; mode=block";
add_header Strict-Transport-Security "max-age=63072000; includeSubDomains";
add_header X-Content-Type-Options nosniff;
add_header Referrer-Policy same-origin;
add_header X-Frame-Options SAMEORIGIN;

# and add customer specific:

add_header Content-Security-Policy "default-src 'self'; base-uri 'none'; font-src 'self' data: https://example.com; frame-ancestors 'self' https://example.com; img-src 'self' data:; object-src 'none'; script-src 'self' unsafe-inline' 'unsafe-eval'; style-src 'self' 'unsafe-inline';"

add_header Permissions-Policy geolocation=();

Notes:
- Having an external frame-ancestor in CSP: X-Frame-Options "SAMEORIGIN" works
- Chrome using F12 shows problems in yellow an red to fix.