我正在Wordpress的前端创建一个可发布的表单（通过一个快捷码）。如果我在没有任何输入的情况下提交此表单，则表单将被罚款。但一旦我在字段中输入数据并发布表单，WordPress就会给出404 Not Found错误。我假设这是某种防止CSRF的措施，但我找不到任何关于如何克服这种行为的文档。

下面是处理短代码的代码：

/**
 * 
 * @param type $atts
 */
public function shortcode_invoice_sales($atts) {
    extract(shortcode_atts(array(
    ), $atts));

    $error = array();
    $user = wp_get_current_user(); // the viewing user

    if (isset($_GET["id"])) {
        $id = (int)$_GET["id"];
        $invoice = new Bbpp_Invoices_Invoice($id);

        if (!$invoice->numInvoices()) {
            return __("Sorry, this invoice does not exist.", "bbpp_invoices");
        }

        if (!$invoice->canView($user->ID)) {
            return __("Sorry, this invoice does not exist.", "bbpp_invoices");
        }
    } else {
        $invoice = new Bbpp_Invoices_Invoice();
        $invoice->addInvoice(array(
            "user_id" => $user->ID,
            "type" => "sale",
            "invoice_date" => date("d/m/Y"),
            "name" => "",
            "invoice_number" => "",
            "method" => "",
            "pay_date" => "",
            "amount" => "",
            "cis_amount" => "",
            "cis_net" => ""
        ));
    }

    if ($_POST) {
        // save the changes to the database
        $data = stripslashes_deep($_POST);

        $invoice->setInvoice($data);
        $error = $invoice->save();
    }

    $html = "";

    $html .= "<style type=\\"text/css\\">";
    $html .= ".bbpp-invoices-input + .bbpp-invoices-input { margin-top: 10px; }";
    $html .= ".bbpp-invoices-form label { width: 150px; margin-right: 15px; display: inline-block; text-align: right; }";
    $html .= ".bbpp-invoices-form input { font-size: 13px; padding: 5px; }";
    $html .= ".bbpp-invoices-form input[type=submit] { font-size: 13px; padding: 5px !important; }";
    $html .= ".bbpp-invoices-hint { font-size: 12px; color: #444; margin-left: 5px; display: inline-block; }";
    $html .= ".bbpp-invoices-prefix { display: inline-block; width: 9px; margin-left: -9px; overflow: hidden; }";
    $html .= "input.bbpp-invoices-currency { width: 70px; }";
    $html .= "</style>";

    if ($id) {
        $html .= "<h3>" . __("Edit Invoice", "bbpp_invoices") . "</h3>";
    } else {
        $html .= "<h3>" . __("New Invoice", "bbpp_invoices") . "</h3>";
    }

    $html .= "<form class=\\"bbpp-invoices-form\\" method=\\"post\\">";

    $html .= "<div class=\\"bbpp-invoices-input\\">";
    $html .= "<label for=\\"bbpp-invoices-input-invoice-date\\">" . __("Invoice Date", "bbpp_invoices") . "</label>";
    $html .= "<input type=\\"text\\" name=\\"invoice_date\\" id=\\"bbpp-invoices-input-invoice-date\\" value=\\"" . esc_attr($invoice->getInvoiceDate()) . "\\">";
    $html .= "<span class=\\"bbpp-invoices-hint\\">dd/mm/yyyy</span>";
    $html .= "</div>";

    $html .= "<div class=\\"bbpp-invoices-input\\">";
    $html .= "<label for=\\"bbpp-invoices-input-name\\">" . __("Customer Name", "bbpp_invoices") . "</label>";
    $html .= "<input type=\\"text\\" name=\\"name\\" id=\\"bbpp-invoices-input-name\\" value=\\"" . esc_attr($invoice->getName()) . "\\">";
    $html .= "<span class=\\"bbpp-invoices-hint\\">" . __("e.g. John Smith", "bbpp_invoices") . "</span>";
    $html .= "</div>";

    $html .= "<div class=\\"bbpp-invoices-input\\">";
    $html .= "<label for=\\"bbpp-invoices-input-invoice-number\\">" . __("Invoice Number", "bbpp_invoices") . "</label>";
    $html .= "<input type=\\"text\\" name=\\"invoice_number\\" id=\\"bbpp-invoices-input-invoice-number\\" value=\\"" . esc_attr($invoice->getInvoiceNumber()) . "\\">";
    $html .= "</div>";

    $html .= "<div class=\\"bbpp-invoices-input\\">";
    $html .= "<label for=\\"bbpp-invoices-input-method\\">" . __("Received Method", "bbpp_invoices") . "</label>";
    $html .= "<input type=\\"text\\" name=\\"method\\" id=\\"bbpp-invoices-input-method\\" value=\\"" . esc_attr($invoice->getMethod()) . "\\">";
    $html .= "</div>";

    $html .= "<div class=\\"bbpp-invoices-input\\">";
    $html .= "<label for=\\"bbpp-invoices-input-pay-date\\">" . __("Date Received", "bbpp_invoices") . "</label>";
    $html .= "<input type=\\"text\\" name=\\"pay_date\\" id=\\"bbpp-invoices-input-pay-date\\" value=\\"" . esc_attr($invoice->getPayDate()) . "\\">";
    $html .= "<span class=\\"bbpp-invoices-hint\\">dd/mm/yyyy</span>";
    $html .= "</div>";

    $html .= "<div class=\\"bbpp-invoices-input\\">";
    $html .= "<label for=\\"bbpp-invoices-input-amount\\">" . __("Invoice Amount", "bbpp_invoices") . "</label>";
    $html .= "<span class=\\"bbpp-invoices-prefix\\">&pound;</span>";
    $html .= "<input type=\\"text\\" name=\\"amount\\" id=\\"bbpp-invoices-input-amount\\" class=\\"bbpp-invoices-currency\\" value=\\"" . esc_attr($invoice->getAmount()) . "\\">";
    $html .= "</div>";

    $html .= "<div class=\\"bbpp-invoices-input\\">";
    $html .= "<label for=\\"bbpp-invoices-input-cis-amount\\">" . __("CIS Amount", "bbpp_invoices") . "</label>";
    $html .= "<span class=\\"bbpp-invoices-prefix\\">&pound;</span>";
    $html .= "<input type=\\"text\\" name=\\"cis_amount\\" id=\\"bbpp-invoices-input-cis-amount\\" class=\\"bbpp-invoices-currency\\" value=\\"" . esc_attr($invoice->getCisAmount()) . "\\">";
    $html .= "</div>";

    $html .= "<div class=\\"bbpp-invoices-input\\">";
    $html .= "<label for=\\"bbpp-invoices-input-cis-net\\">" . __("CIS Net", "bbpp_invoices") . "</label>";
    $html .= "<span class=\\"bbpp-invoices-prefix\\">&pound;</span>";
    $html .= "<input type=\\"text\\" name=\\"cis_net\\" id=\\"bbpp-invoices-input-cis-net\\" class=\\"bbpp-invoices-currency\\" value=\\"" . esc_attr($invoice->getCisNet()) . "\\">";
    $html .= "</div>";      

    $html .= "<div class=\\"bbpp-invoices-input\\">";
    $html .= "<label for=\\"bbpp-invoices-input-submit\\">&nbsp;</label>";
    $html .= "<input type=\\"submit\\" value=\\"" . __("Add new invoice", "bbpp_invoices") . "\\">";
    $html .= "</div>";

    $html .= "</form>";

    return $html;
}