document.referrer & window.opener

Link type	`rel=""`	`rel="noreferrer"`	`rel="noopener"`	`rel="noreferrer noopener"`
`<a>`	same-origin cross-origin	same-origin cross-origin	same-origin cross-origin	same-origin cross-origin
`<a> in about:blank </iframe>`
`window.open`
`<area>`
`<a> in <svg>`
`<math>`	$same-origin$ $cross-origin$	$same-origin$ $cross-origin$	$same-origin$ $cross-origin$	$same-origin$ $cross-origin$