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Cross-origin Resource Sharing (CORS)

an origin is a tuple of protocol:host:port

Access-Control-Allow-Origin: https://x.com:8081 only the specified origin can access

Access-Control-Allow-Origin: * every origin can access

By default, browser XMLHttpRequest or fetch APIs allows same-origin only

Use Access-Control-Allow-Origin to manage CORS

Use integrity to verify a resource is not modified on the way

Use X-Frame-Options: DENY to disallow allow attempts to iframe site

more on CORS