Improper Input Validation in PayTR Virtual POS iFrame API WHMCS Module

The PayTR Virtual Pos iFrame API (v9x) WHMCS Module for payment processing contains a critical input validation vulnerability (CVE-2026-16025). This flaw exists within the module's handling of specified quantities in input data. Attackers can leverage this improper validation to perform input data manipulation during the transaction process. This vulnerability affects all installations of the module from version 9.0.0 through 9.0.2. By manipulating the input fields, an attacker could potentially alter the quantity of items purchased or the associated financial values, impacting the integrity of payment transactions managed through WHMCS. The vendor has addressed this in version 9.0.3.

Impact

Successful exploitation allows for input data manipulation during payment processing. This can lead to financial discrepancies, loss of revenue, and the potential for fraudulent transaction adjustments within the merchant's environment using the affected WHMCS module.

Recommendation

Prioritized actions for administrators:

• Upgrade the PayTR Virtual Pos iFrame API (v9x) WHMCS Module to version 9.0.3 or later immediately to remediate CVE-2026-16025.
• Audit transaction logs for unusual quantity changes or discrepancies in order amounts processed via the PayTR module prior to applying the patch.
• Review payment reconciliation reports to ensure no unauthorized transactions occurred while the vulnerable module was active.