Is there ANY documentation on how to POST lead form data on an external page to Eloqua?

Due to increasing security restrictions in Firefox, I need to update the way we submit data to Eloqua. Previously, this was all done with AJAX, and we just threw out the lack of response that happened due to CORS. But Firefox still sent the data at that point - it "worked," we just didn't really have a way to verify the full exchange completed, it was all trust based. Now, they don't send the data at all, and obviously Oracle isn't gonna do anything about CORS. I'm reworking our form so that it submits to a handler on our side