CVE-2025-13407: 
WordPress vulnerability analysis and mitigation

CVE-2025-13407 is an unauthenticated arbitrary file upload vulnerability in the Gravity Forms WordPress plugin that enables remote code execution (RCE). The flaw affects all versions of Gravity Forms before 2.9.23.1 and stems from insufficient file type validation in the plugin's chunked upload functionality, allowing attackers to upload PHP files to the server. It was published on December 24, 2025, with a CVSS v3.1 base score of 6.8 (Medium), assessed by CISA-ADP (WPScan, Red Hat CVE).

The root cause is classified as CWE-434 (Unrestricted Upload of File with Dangerous Type). The Gravity Forms plugin's chunked upload endpoint (/?gf_page=upload) fails to properly validate or restrict file extensions, allowing PHP files to be submitted through multi-file upload form fields without authentication. Exploitation requires the attacker to first discover or enumerate the server-side upload path where the file is stored before executing it. A public proof-of-concept Python script has been published by WPScan demonstrating the full upload chain using the requests and BeautifulSoup libraries (WPScan).

Successful exploitation allows an unauthenticated attacker to upload arbitrary PHP files to the WordPress server and achieve remote code execution by accessing the uploaded file's URL. This can result in full server compromise, including unauthorized access to sensitive data (high confidentiality impact), modification or deletion of site content and files (high integrity impact), and potential lateral movement within the hosting environment. Availability is not directly impacted by the upload itself, but post-exploitation actions could disrupt service (WPScan, Red Hat CVE).

A public proof-of-concept exploit script is available via WPScan, lowering the barrier for exploitation significantly. The vulnerability is exploitable without authentication, requiring only that the target site has a Gravity Forms page with a multi-file upload field enabled and that the attacker can enumerate the upload path. The EPSS score is approximately 0.058% (0.000580), suggesting currently low observed exploitation probability. No CISA KEV catalog listing or confirmed in-the-wild exploitation campaigns have been reported as of the available data (WPScan, Feedly).

1. Reconnaissance: Identify WordPress sites running Gravity Forms versions prior to 2.9.23.1 using tools like WPScan, Shodan, or manual inspection of plugin version disclosures.
2. Locate a vulnerable form: Browse the target site to find a page containing a Gravity Forms form with the "Enable Multi-File Upload" option enabled (identifiable by the .gform_fileupload_multifile CSS class in the page HTML).
3. Extract form metadata: Parse the page HTML to extract the form ID and file upload field ID from the multi-file upload element's id attribute.
4. Upload malicious PHP file: Send a POST request to /?gf_page=upload with a PHP webshell (e.g., phpinfo.php or a reverse shell) as the file payload, using the chunked upload mechanism. The plugin fails to block PHP file extensions at this stage.
5. Enumerate upload path: Determine the server-side path where the uploaded file was stored — this may be inferred from the server response, common Gravity Forms upload directory conventions (e.g., /wp-content/uploads/gravity_forms/), or directory enumeration tools.
6. Execute the payload: Access the uploaded PHP file via its URL in a browser or HTTP client to trigger remote code execution on the server (WPScan).

• Network: Unexpected POST requests to /?gf_page=upload with .php file extensions in the multipart body; outbound connections from the web server process to unknown external IPs following file upload activity.
• File System: PHP files (e.g., *.php, shell.php, phpinfo.php) present in Gravity Forms upload directories such as /wp-content/uploads/gravity_forms/; newly created files with webshell patterns (e.g., eval(, base64_decode(, system(, passthru().
• Logs: Web server access logs showing POST requests to /?gf_page=upload with unusual file names or content types; subsequent GET requests to PHP files within the Gravity Forms upload directory.
• Process: Unusual child processes spawned by the web server (e.g., php, /bin/sh, curl, wget) not associated with normal WordPress operations.

The vendor has released Gravity Forms version 2.9.23.1, which addresses the file upload validation flaw. All sites running Gravity Forms prior to this version should update immediately via the WordPress admin dashboard or by downloading the patched plugin directly from the vendor. As a temporary workaround, administrators can disable any forms containing multi-file upload fields until the patch is applied, or restrict access to the /?gf_page=upload endpoint via web server rules (e.g., .htaccess or nginx configuration) (WPScan, Red Hat CVE).

WPScan published the vulnerability disclosure along with a full proof-of-concept script on December 24, 2025, providing detailed technical context for the security community. The vulnerability was also noted by INCIBE-CERT (Spain's national cybersecurity incident response team) and tracked by ENISA's EUVD database (EUVD-2025-205034). Community aggregators including Vulners, CIRCL Vulnerability Lookup, and Offseq Radar indexed the CVE shortly after disclosure, indicating moderate security community interest (WPScan, Red Hat CVE).