Contact Form 7 – PayPal & Stripe Add-on <= 2.4.9 - Unauthenticated Payment Bypass via Insufficient Verification of Data Authenticity via PayPal IPN Handler ('invoice'/'mc_gross' Verification)
| CVE | CVE-2026-9189 |
|---|---|
| CVSS | 5.3 (Medium) |
| Publicly Published | May 28, 2026 |
| Last Updated | May 29, 2026 |
| Researcher |
Muni Nitish Kumar Yaddala (Stranger825)
|
Description
The Contact Form 7 – PayPal & Stripe Add-on plugin for WordPress is vulnerable to Payment Bypass via Insufficient Verification of Data Authenticity in all versions up to, and including, 2.4.9. Although `cf7pp_paypal_ipn_handler()` correctly validates IPN authenticity by posting back to PayPal with `cmd=_notify-validate`, it fails to compare the IPN payload's `mc_gross` (payment amount), `mc_currency`, or `receiver_email` fields against the corresponding stored order values before passing the attacker-controlled `invoice` field directly to `cf7pp_complete_payment()`, which marks the order completed after only an integer cast with no amount verification. This makes it possible for unauthenticated attackers to mark arbitrary high-value pending orders as fully paid by making a minimal real PayPal payment and crafting an IPN whose `invoice` parameter references the targeted order, effectively completing purchases without tendering the required payment amount.
References
- plugins.trac.wordpress.org
- plugins.trac.wordpress.org
- plugins.trac.wordpress.org
- plugins.trac.wordpress.org
- plugins.trac.wordpress.org
- plugins.trac.wordpress.org
- plugins.trac.wordpress.org
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Vulnerability Details for Contact Form 7 – PayPal & Stripe Add-on
| Software Type | Plugin |
|---|---|
| Software Slug | contact-form-7-paypal-add-on (view on wordpress.org) |
| Patched? | Yes |
| Remediation | Update to version 2.4.10, or a newer patched version |
| Affected Version |
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| Patched Version |
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Recent vulnerabilities in Contact Form 7 – PayPal & Stripe Add-on
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