MetForm Pro <= 3.9.7 - Unauthenticated Payment Amount Manipulation via 'mf-calculation'
Strategic Overview
- Status
- Patched in 3.9.8
- Affected Plugin
- MetForm Pro
- Affected Version
<= 3.9.7- CVSS
- 5.3Medium
- Weakness type
- CWE-20 · Improper Input Validation
- CVE
CVE-2026-1782
At a glance
CVE-2026-1782 is a medium-severity Improper Input Validation vulnerability in the MetForm Pro WordPress plugin, affecting versions <= 3.9.7. It carries a CVSS score of 5.3 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 3.9.8; sites on affected versions should update now. Disclosed April 2026, reported by andrea bocchetti.
Vulnerability Overview
The MetForm Pro plugin for WordPress is vulnerable to Improper Input Validation in all versions up to, and including, 3.9.7 This is due to the payment integrations (Stripe/PayPal) trusting a user-submitted calculation field value without recomputing or validating it against the configured form price. This makes it possible for unauthenticated attackers to manipulate the payment amount via the 'mf-calculation' field in the form submission REST request granted there exists a specific form with this particular configuration.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site, and no interaction from a victim user.
CWE-20: Improper Input Validation
MetForm Pro <= 3.9.7 carries this weakness at mf-calculation, and reaching it takes no account at all. Improper input validation means the application accepts input without confirming it has the form, type or range the code downstream assumes.
The concrete impact depends on where the unvalidated value lands, which is why records in this class range from cosmetic bugs to full compromise. For MetForm Pro the fix is 3.9.8: builds <= 3.9.7 are affected, anything from 3.9.8 onward is not.
Remediation
Update to version 3.9.8, or a newer patched version
How does WordSec protect against this?
Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: MetForm Pro 3.9.8 closes this, and updating the plugin is the step that ends it.
- Firewall
- Login Security
- Alerts
External References
Related records
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