https://www.bleepingcomputer.com/news/security/monzo-asks-clients-to-reset-pins-after-exposure-to-employees/ > UK-based digital mobile-only bank Monzo asked roughly 480,000 of its customers to change their debit card PINs (personal identification numbers) after discovering that they were stored in encrypted log files. > While Monzo stores customer PINs on a regular basis, the records are kept in a hardened happened part of Monzo's systems that is particularly secure and under tight control when it comes to who has access to them according to the bank.