Source: security@wordfence.com
The Registration, User Profile, Membership, Content Restriction, User Directory, and Frontend Post Submission – WP User Frontend plugin for WordPress is vulnerable to unauthorized loss of data due to a missing capability check on the 'Frontend_Form_Ajax::submit_post' function in all versions up to, and including, 4.2.4. This makes it possible for unauthenticated attackers to delete attachment.
Unauthenticated attackers can exploit a critical vulnerability in the WP User Frontend WordPress plugin to delete attachments, leading to data loss and potential website disruption. This flaw stems from a missing capability check within the plugin's attachment handling functionality, allowing unauthorized users to execute privileged actions.
Step 1: Reconnaissance: The attacker identifies a WordPress website using the vulnerable WP User Frontend plugin (versions up to and including 4.2.4).
Step 2: Payload Creation: The attacker crafts a malicious HTTP POST request to the admin-ajax.php endpoint, which is a standard WordPress AJAX handler. This request targets the Frontend_Form_Ajax::submit_post function.
Step 3: Attachment ID Targeting: The attacker includes the ID of a specific attachment they wish to delete within the POST request parameters. This ID is used by the plugin to identify the file to be removed.
Step 4: Request Submission: The attacker sends the crafted POST request to the vulnerable website. The request does not require authentication.
Step 5: Exploitation: The submit_post function, lacking proper authorization, processes the request and deletes the specified attachment from the server. This results in data loss.
Step 6: Post-Exploitation (Optional): The attacker may attempt to delete multiple attachments, causing further data loss and potentially disrupting the website's functionality.
The vulnerability lies within the Frontend_Form_Ajax::submit_post function of the WP User Frontend plugin. Specifically, the function lacks proper authorization checks before allowing the deletion of attachments. This means that any unauthenticated user can craft a malicious request to the plugin, specifying an attachment ID to be deleted. The function then proceeds to delete the specified attachment without verifying the user's permissions. The root cause is a missing current_user_can() check or similar authorization mechanism before the attachment deletion operation. This allows for unauthorized access and manipulation of the website's data.
While no specific APTs or malware are directly linked to this vulnerability at this time, the ease of exploitation and potential for data loss make it attractive to various threat actors. This vulnerability could be leveraged by attackers for initial access, data destruction, or as part of a larger attack chain. CISA KEV status: Not Applicable (as of the provided date).
Monitor web server access logs for suspicious POST requests to admin-ajax.php targeting the Frontend_Form_Ajax::submit_post function with attachment deletion parameters.
Analyze WordPress database logs for unexpected attachment deletions, especially those originating from unauthenticated users or suspicious IP addresses.
Implement file integrity monitoring (FIM) to detect unauthorized modifications or deletions of attachment files.
Use a Web Application Firewall (WAF) to filter malicious requests based on known attack patterns and signatures (once they become available).
Monitor network traffic for unusual POST requests to the affected endpoint.
Update the WP User Frontend plugin to version 4.2.5 or later. This version likely includes the necessary capability checks to prevent unauthorized attachment deletion.
Implement a Web Application Firewall (WAF) to filter malicious requests.
Review and harden the WordPress configuration, including user roles and permissions.
Regularly back up the website's data, including attachments, to facilitate recovery in case of a successful attack.
Implement a security plugin to monitor for suspicious activity and provide additional protection.
Verify the integrity of all attachments after updating the plugin.