CVE-2026-16038: Unknown Mstore API

Critical severity, CVSS 9.1. EPSS: 0.4% chance of exploitation in the next 30 days.

The MStore API WordPress plugin before 4.21.0 does not verify the payment with the payment gateway before marking an order as paid on several of its payment-completion endpoints, allowing an unauthenticated attacker to mark an arbitrary order fully paid without paying and obtain goods or services for free.

Affected products

• Unknown Mstore API: before 4.21.0 (fixed in 4.21.0)

Published 2026-08-07. Last modified 2026-08-26.