Update or remove extra data from activations

The extra data is tied to the activation data. It cannot be manipulated by you after the fact. So, you have a few options:

1. Deactivate any activations with sensitive data you would like removed.

2. Program your app not to send that data (i.e. don't pass in extra_data)

3. Program your app to send "empty" activation data to clear existing data (use ta.GetExtraData() to locally see if the customer has activation data)

If I re-validate with different extra data, will it overwrite the current extra data? Or is sending empty data the only option?

Yes, you can re-activate with new data and it will replace old data.