I found what is likely an error in our reporting. The page views more than doubled overnight. We went from an average of 47,222 per day to 89,184. This caused the bounce rate to drop from an average of 50.22% to 9.59%. Visits, unique users and conversions were relatively unchanged so I believe those are likely accurate.
The biggest change came from direct traffic, so I thought it may be spam, but we are seeing huge spikes from every traffic channel so something else must be going on too.
We also use Google Analytics and it does not show this happening, so it must be an issue with Adobe, right?
This sounds like there was a change to the Adobe Analytics code on the site. An additional s.t() call was added. Maybe a DTM rule triggering an additional page view. Or some automated tracking of some kind making an additional s.t() call. We might be able to further help if you provide a link to page(s) affected.