Storing data locally is a common task for mobile applications. Such data includes files among other things. One convenient way to store files is to use the external file storage which usually offers a larger amount of disc space compared to internal storage. 

Files created on the external storage are globally readable and writable. Therefore, a malicious application having the permissions `+WRITE_EXTERNAL_STORAGE+` or `+READ_EXTERNAL_STORAGE+` could try to read sensitive information from the files that other applications have stored on the external storage. 

External storage can also be removed by the user (e.g when based on SD card) making the files unavailable to the application.
