Ticket #17737: 17737.4.patch

src/wp-includes/class-wp.php

@@ -261 +261 @@
                         elseif ( isset( $perma_query_vars[$wpvar] ) )
                                 $this->query_vars[$wpvar] = $perma_query_vars[$wpvar];
 
+                        // Discard invalid values that are not supposed to be an array
+                        if ( isset( $this->query_vars[$wpvar] ) && is_array( $this->query_vars[$wpvar] ) ) {
+                                if ( 'post_type' != $wpvar ) {
+                                        unset( $this->query_vars[$wpvar] );
+                                        continue;
+                                }
+                        }
+
                         if ( !empty( $this->query_vars[$wpvar] ) ) {
                                 if ( ! is_array( $this->query_vars[$wpvar] ) ) {
                                         $this->query_vars[$wpvar] = (string) $this->query_vars[$wpvar];