Ticket #35422: wp-login.php.4.patch

src/wp-login.php

@@ -671 +671 @@
 break;
 
 case 'register' :
-        if ( is_multisite() ) {
+        /**
+         * Filter the is_multisite returned value.
+         *
+         * @since 4.5
+         *
+         * @param bool is_multisite().
+         */
+         if ( apply_filters( 'require_wp_signup', is_multisite() ) ) {
                 /**
-                 * Filter the Multisite sign up URL.
+                 * Filter the Multi-site sign up URL.
                  *
                  * @since 3.0.0
                  *
                  * @param string $sign_up_url The sign up URL.
                  */
-                wp_redirect( apply_filters( 'wp_signup_location', network_site_url( 'wp-signup.php' ) ) );
-                exit;
+                if ( wp_redirect( apply_filters( 'wp_signup_location', network_site_url( 'wp-signup.php' ) ) ) ){
+                        exit;
+                };
+
         }
 
         if ( !get_option('users_can_register') ) {