A Quick Overview
There's quite a bit that you should (and will want to) understand about the hack, which you can learn more in a thread on the Adobe CF Admin forum, where a poster first pointed it out on Friday, and I found that I too had been hit.
See the specific thread for more details, including a fairly substantial reply I offered (which he's marked as "the answer"), where I explain more I'd found about it, including how how it got there, how to confirm how it got there for you, how to rectify things, how one might already be protected against it, etc.
The upshot is that a file is put on your server which gives a hacker pretty much unfettered access to a lot of things including reading/downloading/uploading/renaming and creating files, accessing datasource information, and more. The file to look for is called h.cfm and is placed in the CFIDE directory (at least in the current rendition of the hack, which may very likely change when the hacker learns that it's being publicized.) See the forum thread for more on what specifically to look for.
Fortunately for some, the degree to which the hacker would have access to things may be limited by how careful you've been in other protections, such as explained in the various lockdown guides for CF (here for CF10, CF9, and CF8).
I also explain how, despite my own efforts to protect the AdminAPI folder through which the exploit happened, I still fell victim. Perhaps it could happen to others. And it will certainly likely happen to those who have not implemented any protection against that folder (whether blocking access to it by IP address, requiring additional authentication, or otherwise). More in the forum thread.