In short, we do not collect any of your exploration data. All the operations related to third party services are done on your local device. We don't have any server actually. Your data will be uploaded when you sync them with your cloud storages, but only you have access to them. We don’t.
For Dropbox, OneDrive, Nutstore, and iCloud. Fog of World requires the “App Folder” permission, which means your data will be put in a sandbox and Fog of Wolrd only has access to that folder.
However, since Google Drive’s “App Folder” permission doesn’t allow users to access the “App Folder” directly. Fog of World requires Full Google Drive access so users can upload their GPX or KML files and import them to Fog of World later. Your Fog of World data will be stored in Google Drive’s “/Fog of World” folder and Fog of World only reads and writes that folder. None of other folders will be touched by Fog of World.
Here are the more detailed policies of Google Drive usage.