Just to clear the air, lets get an idea
what a .json file is, or is meant to be. Apparently it's related to
Javascript.
Javascript
is not Java, but a language all its own.
The existence of the files is not necessarily dangerous, if no apps use them. But their continued existence on a 'contaminated' device could
pose a threat to the security and functioning of that device inn the future. Getting rid of them is not an overreaction, but a proactive step against a future app installation to potentially read/interpret those files. It's weird to see
such an attack on a rom based device, but apparently the loader script can't tell the difference between a 'computer', and a 'tablet' loading its payload on all devices, and the iPad's local storage makes it just as vulnerable. The Apple ecosystem also seems to provide a new novel way for infections to spread amongst a users many devices. We should all be aware of the potential for that service to be exploited in the future, and hope that Apple has enough safeguards to protect us.
Carry on...