# CVE-2026-81026: MasterStudy LMS payment verification bypass in PayPal IPN handler

Source: https://junglewise.ai/threats/cve-2026-81026-masterstudy-lms-payment-verification-bypass-in-paypal-ipn-handler  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-29. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-81026 · Severity: medium · CVSS 4.8 · Published 2026-08-29

MasterStudy LMS is a WordPress plugin that provides learning management system functionality, including paid course enrollment. The plugin fails to properly validate payment notifications from PayPal, allowing attackers to bypass payment requirements entirely. An unauthenticated attacker can gain full access to paid courses by making only a minimal token payment, causing direct financial loss and unauthorized access to premium educational content.

## Quick answers

**Is CVE-2026-81026 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-81026 being exploited in the wild.

**How severe is CVE-2026-81026?** Medium severity, with a CVSS score of 4.8, published 29 August 2026.

**Which products and versions are affected?** MasterStudy LMS before 3.7.40.

**Is there a fix for CVE-2026-81026?** A patch was published on 2026-08-29: Fixed in version 3.7.40 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-81026 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-81026?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a broken access control issue (CWE-284) in the PayPal Instant Payment Notification (IPN) handler. The plugin accepts payment notifications without verifying the amount, receiver, currency, or payment status against the order details. An unauthenticated attacker can craft a valid IPN callback (using a genuine minimal PayPal payment) with an invoice ID pointing to a full-price order; the plugin marks that order completed without amount validation. No authentication is required, only that a PayPal gateway is configured and a paid course exists. The vulnerability is fixed in version 3.7.40.

## Affected products

- MasterStudy LMS before 3.7.40

## Timeline

- 2026-08-27: disclosed
- 2026-08-29: patched: Fixed in version 3.7.40

## References

- [https://wpscan.com/vulnerability/6677b55c-5d51-4849-ac67-849a500aefe2/](https://wpscan.com/vulnerability/6677b55c-5d51-4849-ac67-849a500aefe2/)