# YITH WooCommerce Product Add-Ons <= 4.35.0 - Unauthenticated Price Manipulation via 'yith_wapo_product_qty' Parameter

- **ID:** WPSEC-2026-3059
- **Plugin:** YITH WooCommerce Product Add-Ons (`yith-woocommerce-product-add-ons`), https://wordpress.org/plugins/yith-woocommerce-product-add-ons/
- **Affected versions:** from 4.0.0 before 4.35.1
- **Fixed in:** 4.35.1 (Update to 4.35.1 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-20
- **Usage among sites WPSec scans:** plugin Medium, affected versions Medium (as of 2026-11-13)
- **Attack surface analysis:** https://attacksurface.wpsec.com/plugin/yith-woocommerce-product-add-ons
- **Fix released:** 2026-11-12
- **Published:** 2026-11-13
- **URL:** https://wpsec.com/vuln/WPSEC-2026-3059/

## Description

The YITH WooCommerce Product Add-Ons plugin for WordPress is vulnerable to price manipulation via the 'yith_wapo_product_qty' parameter in all versions up to, and including, 4.35.0 due to insufficient validation of user-supplied add-on quantities. Posted quantities were stored in the cart item data and used in price calculation for any add-on type without being cast to non-negative integers. This makes it possible for unauthenticated attackers to submit negative or arbitrary quantities to reduce add-on prices and purchase products for less than their intended price.

## References

- https://wpsec.com/vuln/WPSEC-2026-3059/
- https://plugins.svn.wordpress.org/yith-woocommerce-product-add-ons/tags/4.35.1/
- https://wordpress.org/plugins/yith-woocommerce-product-add-ons/

Source: WPSec, https://wpsec.com/vuln/WPSEC-2026-3059/

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.