CVE-2025-13407 is a critical security vulnerability identified in the Gravity Forms WordPress plugin versions prior to 2.9.23.1. The flaw arises from improper validation of file types during the chunked upload process, which allows attackers to upload files with dangerous extensions, specifically PHP scripts. By uploading a malicious PHP file, an attacker can execute arbitrary code on the server hosting the WordPress site, effectively gaining remote code execution (RCE) capabilities. The vulnerability is classified under CWE-434, which concerns unrestricted file upload vulnerabilities that can lead to code execution or other malicious outcomes. Exploitation requires the attacker to discover or enumerate the upload path used by the plugin, which may be feasible through information disclosure or predictable path structures. No CVSS score has been assigned yet, but the vulnerability's impact is severe given the potential for full server compromise. The vulnerability affects all sites running vulnerable versions of Gravity Forms, a popular form plugin used by millions of WordPress sites globally. Although no known exploits have been reported in the wild, the presence of this vulnerability poses a significant risk, especially for sites that accept file uploads from unauthenticated or low-privilege users. The lack of proper file type restrictions in the chunked upload mechanism is the root cause, allowing attackers to bypass typical security controls that prevent uploading executable files. This vulnerability highlights the importance of rigorous input validation and secure file handling in web applications, particularly those that handle user-generated content. Once exploited, attackers can deploy web shells, pivot within the network, steal data, or deface websites. The Gravity Forms plugin is widely used across various sectors, including government, education, and commerce, increasing the potential impact of this vulnerability.

For European organizations, the impact of CVE-2025-13407 can be severe. Successful exploitation can lead to remote code execution on web servers hosting WordPress sites, resulting in full site compromise. This can cause data breaches, defacement, service disruption, and lateral movement within corporate networks. Organizations relying on Gravity Forms for customer interactions, data collection, or internal workflows may face operational disruptions and reputational damage. Sensitive personal data protected under GDPR could be exposed, leading to regulatory penalties and loss of customer trust. The vulnerability also increases the attack surface for ransomware or other advanced persistent threat (APT) actors targeting European entities. Public sector websites, e-commerce platforms, and critical infrastructure providers using WordPress are particularly at risk. The ease of exploitation, combined with the widespread use of the plugin, means that attackers could automate attacks at scale, amplifying the threat across multiple organizations. Additionally, the lack of authentication requirements for exploitation in some scenarios means that external attackers can target vulnerable sites without needing valid credentials, increasing the risk for organizations with publicly accessible forms.

To mitigate CVE-2025-13407, European organizations should immediately plan to update the Gravity Forms plugin to version 2.9.23.1 or later once the patch is released. Until then, organizations should consider disabling the chunked upload functionality if possible or restricting file upload capabilities to trusted users only. Implement strict server-side validation to restrict allowed file types and reject any executable or script files. Employ web application firewalls (WAFs) with rules to detect and block attempts to upload PHP or other dangerous files. Monitor upload directories for unexpected or suspicious files and implement file integrity monitoring to detect unauthorized changes. Restrict access permissions on upload directories to prevent execution of uploaded files, for example by disabling PHP execution in these directories via web server configuration. Conduct regular security audits and vulnerability scans on WordPress installations and plugins. Educate site administrators about the risks of unrestricted file uploads and encourage timely patch management. Finally, implement logging and alerting mechanisms to detect anomalous upload activity or enumeration attempts targeting upload paths.