Critical Vulnerabilities Patched in WHMCS Billing Software for Hosting Providers
WebPros International has disclosed two serious vulnerabilities in its WHMCS billing management platform used by hosting and cloud service providers.
The first flaw, tracked as CVE-2026-67399, is caused by unsafe deserialization of untrusted data. Under specific conditions, it permits unauthenticated attackers to execute arbitrary code on the server, which could lead to full compromise of the installation and related customer data.
The second issue, CVE-2026-67398, affects the 2CheckOut payment gateway module. It results from missing authorization controls and allows unauthenticated access to personal customer details such as names, addresses, email addresses, and telephone numbers.
HackerOne rated CVE-2026-67399 with a CVSS v4.0 base score of 9.3 (Critical) and CVE-2026-67398 with a score of 8.2 (High).
WebPros has released patched versions WHMCS 9.0.8 and 8.13.7 that address both vulnerabilities. Administrators are urged to apply the updates immediately. For CVE-2026-67398, the company also advises temporarily disabling the 2CheckOut module as a workaround until the patch is installed.
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