Login and Registration: Check that `post_password` is a string in `wp-login.php`.

This prevents a fatal error if an array is passed instead.

Follow-up to [19925], [34909], [58023].

Props dd32, swissspidy.
Fixes #61136.
Built from https://develop.svn.wordpress.org/trunk@58093


git-svn-id: http://core.svn.wordpress.org/trunk@57558 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.6-alpha-58092';
+$wp_version = '6.6-alpha-58093';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.

wp-login.php

@@ -753,7 +753,7 @@ switch ( $action ) {
 		break;
 
 	case 'postpass':
-		if ( ! array_key_exists( 'post_password', $_POST ) ) {
+		if ( ! isset( $_POST['post_password'] ) || ! is_string( $_POST['post_password'] ) ) {
 			wp_safe_redirect( wp_get_referer() );
 			exit;
 		}