Nintendo accounts of an unspecified number of users were compromised in the past few days in an attack from an unknown vector, at least for now. Its still unclear why this is happening because the users dont seem to have many things in common, with the exception of their Nintendo credentials. The only hint of something strange going on was a mention on the official Twitter account of Nintendo Japan Support, which said people have been experiencing unauthorized logins and that some of these attackers were accessing users credit card data.”]
Source: https://www.bitdefender.com/blog/hotforsecurity/some-users-lost-access-to-their-nintendo-accounts/