Executive Summary

The Piotnet Forms plugin for WordPress has a vulnerability that allows attackers to upload arbitrary files to the server. This happens because the plugin's 'piotnetforms_ajax_form_builder' function does not properly validate the types of files being uploaded.

The plugin uses an incomplete blacklist of file extensions, blocking only certain types like php, phpt, php5, php7, and exe, but it still allows dangerous extensions such as .phar or .phtml. This flaw enables unauthenticated attackers to upload potentially harmful files.

However, this exploit requires that a file upload field is added to the form on the affected site.

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Impact Analysis

This vulnerability can have severe impacts because it allows unauthenticated attackers to upload arbitrary files to your server.

Such file uploads may lead to remote code execution, meaning attackers could run malicious code on your server, potentially taking control of your website or server environment.

The CVSS score of 9.8 indicates a critical severity, highlighting the high risk of confidentiality, integrity, and availability being compromised.

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Mitigation Strategies

The vulnerability exists in all versions of the Piotnet Forms plugin up to and including 2.1.40 due to missing file type validation allowing dangerous file uploads.

Immediate mitigation steps include updating the Piotnet Forms plugin to a version later than 2.1.40 where this issue is fixed.

Additionally, review and remove any file upload fields in forms that could be exploited, especially if they allow uploading of files with dangerous extensions like .phar or .phtml.

Implement additional server-side file type validation and restrict executable file uploads to prevent arbitrary file uploads.

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Compliance Impact

The vulnerability allows unauthenticated attackers to upload arbitrary files, potentially leading to remote code execution on the affected server. This can result in unauthorized access to sensitive data or disruption of services.

Such unauthorized access or data breaches could negatively impact compliance with common standards and regulations like GDPR and HIPAA, which require protection of personal and sensitive information against unauthorized access and ensure system integrity.

However, the provided information does not explicitly discuss compliance impacts or specific regulatory consequences.

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Detection Guidance

This vulnerability can be detected by checking if the Piotnet Forms plugin for WordPress is installed and if its version is up to and including 2.1.40, as these versions are vulnerable.

To detect potential exploitation attempts, you can monitor your web server logs for unusual file upload requests, especially those attempting to upload files with extensions like .phar or .phtml, which are allowed by the incomplete blacklist.

A practical approach is to search your WordPress installation for the presence of the vulnerable plugin and its version by running commands such as:

• grep -r 'Version' wp-content/plugins/piotnet_forms/
• wp plugin list | grep piotnet_forms

Additionally, to detect suspicious uploaded files, you can run commands to find files with dangerous extensions in your uploads directory, for example:

• find wp-content/uploads/ -type f \( -name '*.phar' -o -name '*.phtml' \)

Monitoring HTTP requests for POST requests to endpoints related to 'piotnetforms_ajax_form_builder' with file uploads can also help detect exploitation attempts.

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