Improper Input Validation in Ninja Forms WordPress Plugin

Executive Summary

This vulnerability in the Ninja Forms WordPress plugin allows unauthenticated attackers to manipulate form calculations and payment totals by injecting arbitrary numeric values. The issue occurs due to improper input validation in the get_calc_value() method for ListSelect and ListRadio fields, causing it to fail open and return attacker-controlled values. This enables bypassing pricing logic and setting payment amounts to zero or arbitrary figures.

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Detection Guidance

Check if your Ninja Forms plugin version is 3.14.8 or earlier. Inspect form submissions to the ajax submit endpoint for tampered numeric values in ListSelect or ListRadio fields. Monitor for unexpected payment amount changes or zero totals.

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Impact Analysis

If you use the affected Ninja Forms plugin versions, attackers could manipulate form submissions to alter payment amounts, potentially leading to financial losses or unauthorized transactions. The vulnerability allows bypassing pricing logic, enabling attackers to set prices to zero or arbitrary values without proper validation.

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Compliance Impact

This vulnerability could lead to non-compliance with GDPR or HIPAA by enabling unauthorized data or financial manipulation through tampered form submissions. It undermines integrity controls required for handling sensitive data, potentially violating regulatory requirements for data accuracy and security.

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Mitigation Strategies

Update the Ninja Forms plugin to version 3.14.9 or later immediately. Review recent form submissions for suspicious activity. Implement input validation for form fields to reject unexpected numeric values.

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