The file contains data about your latitude and longitude along with the timestamp. This information can be easily accessed by jailbreaking the phone, unfortunately, on the computer even without that. Moreover, the file is not encrypted and can be read by just anyone using a simple app.
Apple is yet to comment on this issue. If it really is a bug, Apple is likely going to fix it in the next iOS update. Temporarily, so you can use untrackerd App, it is available on Cydia to prevent your iPhone from recording all your locations.