diff -r 3d4e9c994f10 -r a86126ab1dd4 wp/wp-includes/Requests/Cookie.php
--- a/wp/wp-includes/Requests/Cookie.php	Tue Oct 22 16:11:46 2019 +0200
+++ b/wp/wp-includes/Requests/Cookie.php	Tue Dec 15 13:49:49 2020 +0100
@@ -288,6 +288,11 @@
 				return $expiry_time;
 
 			case 'domain':
+				// Domains are not required as per RFC 6265 section 5.2.3
+				if (empty($value)) {
+					return null;
+				}
+
 				// Domain normalization, as per RFC 6265 section 5.2.3
 				if ($value[0] === '.') {
 					$value = substr($value, 1);