1. Cross-Origin Resource Sharing

    Method of performing XMLHttpRequests across domains

  2. eventsource api: `eventsource()` constructor: cors support (`withcredentials`)

  3. fetchevent api: respondwith: `networkerror` thrown if the request mode is `same-origin` and the response type is `cors`

  4. headers http header: content-length: cors-safelisted response header