Arbitrary Shortcode Execution in Formidable Forms WordPress Plugin

Executive Summary

This vulnerability in the Formidable Forms WordPress plugin before version 6.35 allows unauthenticated visitors to execute arbitrary shortcodes on pages displaying affected forms. The issue occurs because the plugin does not properly sanitize request-derived values when substituting tokens like [entry_key] into custom HTML, enabling attackers to inject malicious shortcodes with chosen attributes.

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Detection Guidance

Check if your Formidable Forms plugin version is below 6.35 by inspecting the plugin files or WordPress admin panel. Look for forms with custom HTML blocks containing the [entry_key] token, as this is required for exploitation.

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Impact Analysis

An attacker could exploit this to execute server-side code on your website, potentially leading to unauthorized access, data theft, or defacement. Since no authentication is required, any visitor could trigger the attack if your site uses a vulnerable version of the plugin and has manually added the [entry_key] token to a form's custom HTML.

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Compliance Impact

This vulnerability could lead to unauthorized data access or modification, violating GDPR's integrity and confidentiality principles or HIPAA's security requirements. A successful exploit may result in data breaches, triggering compliance violations and potential legal penalties.

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Mitigation Strategies

Update the Formidable Forms plugin to version 6.35 or later immediately. Remove any custom HTML blocks containing the [entry_key] token from your forms if present.

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