The Dictionary app in Apple OS X before 10.10.5 does not use HTTPS, which allows man-in-the-middle attackers to obtain sensitive information by sniffing the network or spoof word definitions by modifying the client-server data stream.
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.