wp-includes/http.php:687Marks allowed redirect hosts safe for HTTP requests as well.
$is_externalbool$hoststringboolfunction allowed_http_request_hosts( $is_external, $host ) { if ( ! $is_external && wp_validate_redirect( 'http://' . $host ) ) { $is_external = true; } return $is_external;}Introduced in 3.6.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/http.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.