The "challengeMandated" parameter indicates whether a challenge (additional authentication) is required for the respective transaction from a regulatory perspective.
For example, this is the case for customer-initiated, initial transactions.
However, the card-issuing bank can also trigger a challenge if this is not required from a regulatory point of view.
The "transStatus" parameter, which is assigned the value "C" by the bank server in the case of a challenge, is therefore decisive.