r - DeployR Open - Restrict file system access -

according deployr documentation each session locked down:

"by default, r sessions executing on deployr grid not authorized access files or directories outside of r working directory"

however, have been able upload simple script using user has basic_user role , reads file c:\ drive on windows.

t <- read.table("c:\\myfile.csv") t 

how lock down access file system? seem have missed something.