Version 4.2.0 is a very special version for the Bitcoin and Altcoin Wallets WordPress plugin: The JSON API can now be accessed via a key. The JSON API is what allows a user to view their wallets, to query past transactions, and to initiate requests for new transactions.
This is mainly of interest to developers, as it makes programmatic access easier. Previously, it was not possible to access the JSON API without logging in to WordPress and storing cookies in memory or in a file. Now, it is possible to access the API via a key. The key can be passed as a GET parameter or, preferably, via an HTTP header.
The feature is disabled by default. To enable it for certain users, grant them the access_wallets_api capability. If you wish to do this for a user role, you may do so via the Capabilities menu under Wallets. A random key is assigned to each user with the necessary capability.
This authentication method is only available to JSON API version 3. Older versions of the API do not support this feature and can only be accessed with cookie-based authentication.
Users can view, and refresh, their API key via the [wallets_api_key] shortcode. Refreshing a key means that the old key is invalidated.
Additionally, the API key is shown in the user profile section. The key is shown only to the user, and to any admin with the manage_wallets capability.
To see more information and examples of how to use this feature, consult the accompanying documentation under APIs → Wallets → JSON API → Programmatic access to the Transactions API.