# Quick PayPal Payments <= 6.0.3 - Unauthenticated Payment Amount Manipulation via Payment Form Parameters

- **ID:** WPSEC-2026-0943
- **Plugin:** Quick PayPal Payments: Payment Button & Form (`quick-paypal-payments`), https://wordpress.org/plugins/quick-paypal-payments/
- **Affected versions:** all versions before 6.0.4
- **Fixed in:** 6.0.4 (Update to 6.0.4 or later.)
- **Severity:** Medium 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N)
- **Weakness:** CWE-472
- **Usage among sites WPSec scans:** plugin Low, affected versions None seen (as of 2026-10-14)
- **Attack surface analysis:** https://attacksurface.wpsec.com/plugin/quick-paypal-payments
- **Fix released:** 2026-10-12
- **Published:** 2026-10-14
- **URL:** https://wpsec.com/vuln/WPSEC-2026-0943/

## Description

The Quick PayPal Payments plugin for WordPress is vulnerable to Payment Amount Manipulation via the payment form submission (the qpp_validate_form AJAX action and the [qpp] shortcode form post) in all versions up to, and including, 6.0.3. This is due to the plugin taking pricing data from the submitted form: price-setting shortcode attributes were posted back as unsigned fields, a posted field skipped validation, a posted form value switched which form's prices applied, loosely compared values matched a fixed price option, a quantity of zero was accepted on forms without a quantity field, and a crafted item amount lowered a subscription's per-period price. This makes it possible for unauthenticated attackers to pay less than the configured price and have the payment recorded as paid; since 5.7.51 the forged price is also stored as the amount the IPN check expects.

## References

- https://wpsec.com/vuln/WPSEC-2026-0943/
- https://plugins.svn.wordpress.org/quick-paypal-payments/tags/6.0.4/
- https://wordpress.org/plugins/quick-paypal-payments/

Source: WPSec, https://wpsec.com/vuln/WPSEC-2026-0943/

License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Free to use, share and adapt, also commercially, if you credit WPSec and link to this advisory.