Complex sentence: The PIN harvesting can be performed with a chip skimmer as a tampered CVM list, which downgrades the cardholder verification method to offline PIN, is still honoured by POS terminals despite its signature being invalid.
Split into simpler sentences: The PIN harvesting can be performed with a chip skimmer. In essence, a CVM list that has been modified to downgrade the CVM to Offline PIN is still honoured by POS terminals despite its signature being invalid.