Researchers at the University of Glasgow found that cloud storage apps that say they send files to the cloud also leave retrievable versions of files on the devices. They tested some cloud-based file storage systems tested included Box, Dropbox and SugarSync on HTC Desire, running Android 2.1, and an iPhone 3S running iOS 3.3. They found that Smartphone devices which access cloud storage services can potentially contain a proxy view of the data stored in a cloud storage service. The recovery of cache data from these devices can in some scenarios provide access to further data stored.
Source: https://thehackernews.com/2013/03/smartphones-cache-poses-huge-risk-for_27.html