CVE-2026-83537

Express Checkout <= 2.4.0 - Unauthenticated Payment Bypass

2026-09-07 00:00

Strategic Overview

Status: Patched in 2.5.0
Affected Plugin: WP Express Checkout (Fast Payments via PayPal & Stripe)
Affected Version: <= 2.4.0
CVSS: 5.3Medium
Weakness type: CWE-602 · Client-Side Enforcement of Server-Side Security
CVE: CVE-2026-83537

View all WP Express Checkout (Fast Payments via PayPal & Stripe) vulnerabilities

At a glance

CVE-2026-83537 is a medium-severity Client-Side Enforcement of Server-Side Security vulnerability in the WP Express Checkout (Fast Payments via PayPal & Stripe) WordPress plugin, affecting versions <= 2.4.0. It carries a CVSS score of 5.3 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 2.5.0; sites on affected versions should update now. Disclosed September 2026, reported by Ryan Zegar.

Vulnerability Overview

The Express Checkout plugin for WordPress is vulnerable to Payment Bypass in all versions up to, and including, 2.4.0. This is due to a lack of server-side payment verification. This makes it possible for unauthenticated attackers to bypass payments.

Technical Analysis

The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site, and no interaction from a victim user.

CWE-602: Client-Side Enforcement of Server-Side Security

The product is composed of a server that relies on the client to implement a mechanism that is intended to protect the server.

Remediation

Update to version 2.5.0, or a newer patched version

How does WordSec protect against this?

This one needs no account at all, which puts it outside what login hardening can reach; WordSec's login security narrows the account-level paths around it, and the firewall is what inspects the request itself. None of that substitutes for the fix: WP Express Checkout (Fast Payments via PayPal & Stripe) 2.5.0 closes this, and updating the plugin is the step that ends it.

Login Security
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2026-83537 https://www.wordfence.com/threat-intel/vulnerabilities/id/74df81cd-8cea-4545-86d0-eea2fdf75457 https://nvd.nist.gov/vuln/detail/CVE-2026-83537

Related records

Same weakness class

5.3CVE-2026-83533: Express Checkout <= 2.4.8 Payment BypassCVE-2026-83533

Other vulnerabilities in WP Express Checkout (Fast Payments via PayPal & Stripe)

CVSS Vector

5.3

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Base

Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone
User InteractionNone
ScopeUnchanged
ConfidentialityNone
IntegrityLow
AvailabilityNone

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