This article about master keys, which also features the MasterCard [tm] logo, is written by the same journalist who called skeptics "detractors" in the git master affair.
Way back when I worked at a bank we stored the TMK for the ATM's in the clear in Cobol source ... needless to say after an audit finding from Visa we soon got a HSM.
Disclaimer: I'm a South African living in the UK and yes, I know I'm generalising - excessively.
Jolly Sarf Africans! Light-fingered larcenists - can't leave them alone with anything these days! ;-)