The vulnerability identified as CVE-2026-0939 affects the Rede Itaú for WooCommerce plugin, a WordPress extension facilitating payment processing via PIX, credit card, and debit card methods. The core issue is an insufficient verification of data authenticity (CWE-345) in the payment callback mechanism. When a payment is processed, the payment gateway sends a callback to the WooCommerce system to update the order status. The plugin fails to properly verify that these callbacks are genuinely from Rede Itaú, allowing unauthenticated attackers to forge or manipulate callback data. This manipulation can result in changing order statuses arbitrarily, such as marking unpaid orders as paid or marking paid orders as failed. The vulnerability requires no privileges or user interaction and can be exploited remotely over the network. All versions up to 5.1.2 are affected, and no patches have been published at the time of disclosure. The CVSS v3.1 base score is 5.3, reflecting a network attack vector with low complexity, no privileges required, no user interaction, and an impact limited to integrity. No known exploits have been reported in the wild yet. The plugin’s failure to authenticate callback data undermines the trustworthiness of transaction records, potentially enabling financial fraud, revenue loss, and reputational damage for affected merchants.

For European organizations using WooCommerce with the Rede Itaú payment plugin, this vulnerability can lead to fraudulent manipulation of order statuses. Attackers could mark unpaid orders as paid, causing merchants to ship goods or provide services without receiving payment, resulting in direct financial losses. Conversely, marking paid orders as failed could disrupt legitimate transactions, harming customer experience and trust. The integrity of transaction data is compromised, which can affect accounting, auditing, and compliance processes. Since the vulnerability does not affect confidentiality or availability, data breaches or service outages are less likely. However, the financial and reputational impact can be significant, especially for e-commerce businesses relying on accurate payment processing. The risk is heightened in sectors with high transaction volumes or where Rede Itaú payment methods are commonly used. Additionally, the lack of authentication in callbacks could be exploited as part of larger fraud schemes or to undermine competitive businesses.

Immediate mitigation involves monitoring and validating payment callbacks manually or through custom code that verifies callback authenticity, such as checking digital signatures, IP whitelisting, or using secure tokens if supported by Rede Itaú. Merchants should restrict plugin usage to trusted environments and limit exposure by disabling the plugin if not in use. It is critical to apply any forthcoming official patches from the vendor promptly. Until patches are available, organizations can implement Web Application Firewall (WAF) rules to detect and block suspicious callback requests. Logging and alerting on unexpected order status changes can help detect exploitation attempts early. Additionally, merchants should review and tighten WooCommerce order management workflows to require secondary verification for status changes. Regular backups and transaction audits will assist in recovery and forensic analysis if exploitation occurs. Engaging with the plugin vendor and monitoring security advisories is essential to stay informed about updates and fixes.