diff --git a/wp-includes/user.php b/wp-includes/user.php
index 700a7589..4fbb9df9 100644
--- a/wp-includes/user.php
+++ b/wp-includes/user.php
@@ -51,7 +51,7 @@ function wp_signon( $credentials = array(), $secure_cookie = '' ) {
 		if ( ! empty( $_POST['log'] ) ) {
 			$credentials['user_login'] = wp_unslash( $_POST['log'] );
 		}
-		if ( ! empty( $_POST['pwd'] ) ) {
+		if ( ! empty( $_POST['pwd'] ) && is_string( $_POST['pwd'] ) ) {
 			$credentials['user_password'] = $_POST['pwd'];
 		}
 		if ( ! empty( $_POST['rememberme'] ) ) {