Further questions:

1. How does one upgrade to WebPayment SDK? I assume this is done in Square itself. Wondering if I should set up a new Application in Square and use that for my testing in my upgraded to 1.5.7d store.

2. Is the square module that's part of 1.5.7d compatible with WebPayment SDK or do I need to install some different ZC plugin for this? I didn't see anything in the plug-in repository so I'm guessing not.