Description
This article describes the warning received from GUI when a firmware upgrade is processed from GUI.
This Warning is generally to caution that if the upgrade path is not followed, it will give corrupt output
Scope
FortiGate.
Solution
Below is the warning for perusal.

As the firmware is downloaded and uploaded, it will throw this error even if the upgrade path is correct or accurate.
Hence it is recommended to verify the upgrade path and in case if the upgrade path is correct, ignore the warning and proceed for upgrade.
Hence it is recommended to verify the upgrade path and in case if the upgrade path is correct, ignore the warning and proceed for upgrade.
Check the upgrade path: