CVE-2020-36731 in Flexible Checkout Fields for WooCommerce Plugin
Summary
by MITRE • 06/07/2023
The Flexible Checkout Fields for WooCommerce plugin for WordPress is vulnerable to Unauthenticated Arbitrary Plugin Settings update, in addition to Stored Cross-Site Scripting in versions up to, and including, 2.3.1. This is due to missing authorization checks on the updateSettingsAction() function which is called via an admin_init hook, along with missing sanitization and escaping on the settings that are stored.
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Analysis
by VulDB Data Team • 07/05/2023
The Flexible Checkout Fields for WooCommerce plugin presents a critical security vulnerability that affects WordPress environments through an unauthenticated arbitrary plugin settings update mechanism. This vulnerability exists within the plugin's updateSettingsAction() function which is triggered through the admin_init hook, creating a pathway for malicious actors to manipulate plugin configurations without proper authentication. The flaw resides in the absence of authorization checks that should normally validate user credentials and permissions before allowing modifications to plugin settings. This oversight enables attackers to execute unauthorized changes to the plugin's configuration parameters, potentially compromising the entire checkout process and customer data handling within WooCommerce implementations.
The technical exploitation of this vulnerability combines multiple attack vectors that amplify its impact on affected systems. The missing sanitization and escaping mechanisms on stored settings create a stored cross-site scripting vulnerability that allows attackers to inject malicious scripts into the plugin's configuration storage. This dual vulnerability creates a particularly dangerous scenario where an attacker can first modify plugin settings through the unauthenticated update function and then leverage the stored XSS to execute malicious code in the context of administrator sessions. The combination of these flaws means that even a basic unauthenticated user can gain significant control over the checkout functionality and potentially access sensitive customer information.
The operational impact of CVE-2020-36731 extends beyond simple configuration changes to potentially compromise entire e-commerce operations and customer data integrity. Attackers exploiting this vulnerability can modify checkout field configurations to redirect customer data to malicious endpoints, alter payment processing workflows, or inject malicious code that persists across multiple user sessions. The stored XSS component particularly threatens administrators who may unknowingly visit compromised pages, as it can lead to session hijacking, privilege escalation, or complete system compromise. Organizations running affected versions of the plugin face risks including data theft, financial fraud, and reputational damage from compromised customer checkout experiences.
Security mitigations for this vulnerability require immediate action from affected organizations to prevent exploitation. The most critical step involves upgrading to a patched version of the Flexible Checkout Fields for WooCommerce plugin that implements proper authorization checks on the updateSettingsAction() function and applies adequate sanitization and escaping to all stored settings. Organizations should also implement network-level monitoring to detect suspicious administrative activity and consider implementing web application firewalls to block known attack patterns targeting WordPress plugins. Additionally, regular security audits of installed plugins should include verification of proper input validation and authorization mechanisms, as this vulnerability demonstrates how missing security controls in individual components can create systemic risks for entire WordPress installations. The vulnerability aligns with CWE-862, which addresses insufficient authorization, and represents a clear violation of the principle of least privilege that should govern all administrative functions within web applications.