REDCap before 5.0.4 and 5.1.x before 5.1.3 does not reject certain undocumented syntax within branching logic and calculations, which allows remote authenticated users to bypass intended access restrictions via (1) the Online Designer or (2) the Data Dictionary upload, as demonstrated by an eval call.
http://ctsi.psu.edu/wp-content/uploads/2013/03/REDCap-Release-Notes-Version5.pdf