David Litchfield was one of the top bug hunters in the game and specialized in causing large-scale headaches for Oracle. He recently decided to resurface, which is good news for the security community and users but may not cause a celebration among Oracle engineers. After taking a long break from security research and spending a lot of time in close proximity to great white sharks, he began looking at Oracle s security again. He found several methods for bypassing the data redaction service and tricking the system into returning data that should be masked.
Source: https://threatpost.com/oracle-database-redaction-trivial-to-bypass/107631/