FOSSBilling is an open source billing and client-management platform. From 0.8.4 until 0.8.6, hasManagePermission fails open for inactive non-core modules because its early return on !isExtensionActive skips the module-access and manage_settings checks. A low-privileged staff account with module-level extension access targets a deactivated non-core module through extension/config_get or extension/config_save. The account can call api/admin/extension/config_get or api/admin/extension/config_save for a deactivated non-core module to read decrypted retained extension secrets and overwrite stored extension configuration. The getConfig function returns the decrypted stored configuration despite the module's inactive state. This residual path remained after the earlier CVE-2026-62962 authorization fix. This issue is fixed in version 0.8.6.