71

Issuer Script Template 1 is the delivery vehicle for post-issuance commands the issuer wants the card to execute before the transaction's second GENERATE AC - the mechanism that lets an issuer reach into a card that's already out in the field and change something (unblock a PIN, update a risk parameter, block the card entirely) using the current online transaction as the carrier, since there's no other channel to talk to an offline chip card directly. It's related to its sibling, Issuer Script Template 2 (72), which carries the same kind of content but timed for after the second GENERATE AC instead of before, and to the Issuer Script Command (86) that actually names what to do - 71 itself is just the timing wrapper, not the instruction. Because script processing happens inside the transaction itself, a script that fails partway through is exactly the condition the related Issuer Action Codes (9F0D/9F0E/9F0F) can flag via their own script-failure bits, tying an entire post-issuance-messaging subsystem back into the same risk-management framework the rest of the transaction already uses. See EMV 4.4 Book 3.