CVE-2026-85520 in Google Merchant Center Feed
Summary
by MITRE • 09/29/2026
Google Merchant Center Feed (gmfeed) module for PrestaShop is vulnerable to unauthenticated arbitrary file write in the feed.php endpoint. An unauthenticated attacker can send a crafted request that controls the output file name, path, extension, and content through request parameters. Due to the lack of authentication and input validation, the request is processed successfully, allowing an attacker to write and execute arbitrary PHP code, resulting in remote code execution (RCE).
This issue was fixed in version 2.3.9.
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Analysis
by VulDB Data Team • 09/29/2026
The Google Merchant Center Feed module for PrestaShop contains a critical security vulnerability within its gmfeed component that allows unauthenticated attackers to achieve Remote Code Execution on the target server. This flaw resides specifically in the feed.php endpoint, which is designed to generate and serve product feeds but fails to implement necessary access controls or input sanitization mechanisms. The absence of authentication checks means that any user with network connectivity to the web application can interact directly with this functionality without providing valid credentials. Furthermore, the module lacks robust validation for parameters passed via HTTP requests, specifically those controlling file output operations. This combination of missing authorization and insufficient input validation creates a severe attack vector where an attacker can manipulate server-side file system interactions through crafted request parameters.
The technical nature of this vulnerability is classified as an arbitrary file write flaw that escalates to remote code execution due to the specific context of PHP-based web applications. An unauthenticated actor can send a specially constructed HTTP request containing maliciously formatted parameters for output filename, directory path, file extension, and content payload. Because the application processes these inputs without verifying their legitimacy or sanitizing special characters, it writes the attacker-controlled data directly into the server's filesystem. By carefully selecting the file extension to be .php and embedding executable PHP code within the content parameter, the attacker ensures that the written file is interpreted as a script by the web server rather than treated as static text or structured feed data. This effectively places a backdoor shell on the server, granting the attacker full control over the underlying operating system through the web service context.
From an operational perspective, this vulnerability poses an existential threat to any PrestaShop store utilizing the affected version of the Google Merchant Center Feed module prior to patching. Successful exploitation allows attackers to compromise the integrity and confidentiality of the entire e-commerce platform. Beyond gaining initial access via RCE, adversaries can use the foothold to exfiltrate sensitive customer data including credit card information, personal identifiable information, and order histories stored in the associated database. They may also install additional malware such as web shells for persistent access, modify product listings to facilitate phishing or fraud, or pivot into other internal network segments if the server is part of a larger infrastructure. The impact extends beyond technical compromise to include significant reputational damage, regulatory penalties under data protection laws like GDPR, and loss of customer trust.
This vulnerability aligns with CWE-434 which describes the danger of unrestricted upload of files with dangerous types, although in this specific case it is driven by parameter manipulation rather than a traditional file upload interface. It also maps to ATT&CK technique T1505.003 known as Web Shell, where attackers deploy malicious scripts to maintain access and execute commands on compromised systems. The lack of authentication corresponds to CWE-287 involving improper authentication mechanisms that allow unauthorized actors to perform privileged actions. Understanding these mappings helps security teams prioritize remediation efforts based on established industry frameworks for vulnerability management and risk assessment.
To mitigate this threat, organizations must immediately upgrade the Google Merchant Center Feed module to version 2.3.9 or later where the issue has been resolved by implementing strict input validation and ensuring that file output operations are restricted to safe directories with controlled naming conventions. Administrators should also verify that no unauthorized PHP files exist in public-facing web directories as a forensic step following potential exposure. Implementing Web Application Firewalls can provide an additional layer of defense by blocking requests containing suspicious patterns associated with path traversal or code injection attempts. Regular security audits and penetration testing focused on file handling functionalities are recommended to detect similar weaknesses across the application ecosystem before they can be exploited in production environments.