    public function action_edge_mode_enable() {
        w3_require_once(W3TC_INC_FUNCTIONS_DIR . '/activation.php');
        $config_path = w3_get_wp_config_path();

        $config_data = @file_get_contents($config_path);
        if ($config_data === false)
            return;

        $new_config_data = $this->wp_config_evaluation_mode_remove_from_content($config_data);
        $new_config_data = preg_replace(
            '~<\?(php)?~',
            "\\0\r\n" . $this->wp_config_evaluation_mode(),
            $new_config_data,
            1);

        if ($new_config_data != $config_data) {
            try {
                w3_wp_write_to_file($config_path, $new_config_data);
            } catch (FilesystemOperationException $ex) {
                throw new FilesystemModifyException(
                    $ex->getMessage(), $ex->credentials_form(),
                    'Edit file <strong>' . $config_path .
                    '</strong> and add the next lines:', $config_path,
                    $this->wp_config_evaluation_mode());
            }
            try {
                $this->_config_admin->set('notes.edge_mode', false);
                $this->_config_admin->save();
            } catch (Exception $ex) {}
        }
        w3_admin_redirect(array('w3tc_note' => 'enabled_edge'));
    }
The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request.