CVE-2007-4143 in phpCoupon
Summary
by MITRE
user.php in the Billing Control Panel in phpCoupon allows remote authenticated users to obtain Premium Member status, and possibly acquire free coupons, via a modified URL containing a certain billing parameter and REQ=auth, status=success, and custom=upgrade substrings, possibly related to PayPal transactions.
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Analysis
by VulDB Data Team • 11/12/2025
The vulnerability described in CVE-2007-4143 resides within the billing control panel of phpCoupon, a web-based coupon management system that was widely used in e-commerce environments during the mid-2000s. This issue represents a critical authorization bypass flaw that allows authenticated users to manipulate system parameters and gain unauthorized premium membership privileges. The vulnerability specifically affects the user.php script which handles billing operations and membership status updates within the application's control panel.
The technical exploitation of this vulnerability occurs through manipulation of HTTP request parameters within the billing control panel. Attackers can construct modified URLs that contain specific substrings including REQ=auth, status=success, and custom=upgrade which are typically used during legitimate PayPal transaction processing. When these parameters are altered or injected into the billing flow, the system fails to properly validate the authenticity of the transaction status update, allowing attackers to bypass normal authorization checks. This flaw stems from inadequate input validation and parameter sanitization within the billing processing logic, enabling attackers to manipulate the membership upgrade process without proper authentication or authorization.
The operational impact of this vulnerability extends beyond simple privilege escalation to potentially enable financial fraud within the phpCoupon ecosystem. Successful exploitation allows attackers to obtain premium member status without paying the required fees, which could lead to unauthorized access to premium features and services. More critically, the vulnerability may enable attackers to acquire free coupons, representing a direct financial loss to the system administrators and potentially affecting the entire business model of coupon distribution. The attack vector requires only authenticated access to the system, making it particularly dangerous as it can be exploited by users who already have legitimate access but with malicious intent.
This vulnerability aligns with CWE-284, which describes improper access control in software systems, and demonstrates how weak parameter validation can lead to unauthorized privilege escalation. The attack pattern corresponds to techniques found in the ATT&CK framework under privilege escalation and credential access categories. The issue highlights fundamental security flaws in the application's trust model, where the system incorrectly assumes that legitimate transaction parameters indicate valid authorization. Organizations using phpCoupon or similar systems should implement proper parameter validation, input sanitization, and transaction status verification mechanisms to prevent such manipulations. Additionally, the vulnerability underscores the importance of proper session management and authorization checks in web applications, particularly those handling financial transactions and membership upgrades.