From the article posted 06 Oct 2014 at Digital Reader.
Here.
Adobe isn’t just tracking what users are doing in DE4; this app was also scanning my computer, gathering the metadata from all of the ebooks sitting on my hard disk, and uploading that data to Adobe’s servers.
In. Plain. Text.
And just to be clear, this includes not just ebooks I opened in DE4, but also ebooks I store in calibre and every Epub ebook I happen to have sitting on my hard disk.