Others have covered this, but I also added a Kbase article (just now) that offers more information about what a privileged helper tool is, and why we use one: What is CCC's Privileged Helper Tool? | Carbon Copy Cloner | Bombich Software
It's definitely not new, we've been using a PHT for 9 years now; since Snow Leopard. But you're really seeing it now because Mojave requires you to grant it full disk access. It's frustrating to us that Apple is forcing you to do this manually vs. having a dialog in which you could immediately grant access. I actually spoke with the Privacy team at Apple's developer conference and made a case for a dialog. They insisted on the laborious method, they want it to be more difficult. So here we are, now you're forced to take a look at CCC's underwear.
The level of access that you're granting to CCC is also not new, CCC has had (and required) that level of access all along. We can't make a backup of your startup disk and all of your data without being able to read those files.
Mike
Bombich Software, Inc.