Executive brief
J2Store is a popular Joomla extension that turns a Joomla website into an online store with payment processing. A vulnerability in the PayPal payment notification handler allows an attacker to craft a malicious link that, when clicked by a customer or loaded by an automated system, injects attacker-chosen parameters into the checkout confirmation page. While this does not directly expose data or compromise accounts on its own, it could be chained with other techniques to manipulate the checkout flow or mislead users.
Technical details
The vulnerability is a parameter injection/smuggling flaw in the PayPal notify endpoint of J2Store's checkout controller. Unescaped request data from a crafted link is reflected into a redirect response, allowing an attacker to inject arbitrary query parameters into the follow-up checkout confirmation request. The attack requires social engineering (convincing a user to click the malicious link), and the injected parameters are limited to what the checkout controller already accepts. The vulnerability affects J2Store versions 1.0.0–3.3.2, 4.0.0–4.0.22, and 4.1.0–4.1.7. No active exploitation in the wild has been reported.
Affected products
- j2commerce.com J2Store 1.0.0–3.3.2, 4.0.0–4.0.22, 4.1.0–4.1.7
Timeline
- 2026-09-15: disclosed