    private function entityInAttributeValueState() {
        // Attempt to consume an entity.
        $entity = $this->entity();

        // If nothing is returned, append a U+0026 AMPERSAND character to the
        // current attribute's value. Otherwise, emit the character token that
        // was returned.
        $char = (!$entity)
            ? '&'
            : $entity;

        $last = count($this->token['attr']) - 1;
        $this->token['attr'][$last]['value'] .= $char;
    }
The software does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.