Ticket #35069: 35069-2.diff

src/wp-includes/pluggable.php

@@ -237 +237 @@
 
         /**
          * Filter the wp_mail() arguments.
+         * Expects a return array. If an array is not returned, we'll bail here
+         * and assume that wp_mail has been short-circuited.
          *
          * @since 2.2.0
          *
@@ -245 +247 @@
          */
         $atts = apply_filters( 'wp_mail', compact( 'to', 'subject', 'message', 'headers', 'attachments' ) );
 
+        if ( ! is_array( $atts ) ) {
+           return $atts;
+        }
+
         if ( isset( $atts['to'] ) ) {
                 $to = $atts['to'];
         }