USB port as in "for charging of personal devices"
or
USB port as in "attach your own storage for playing something on the IFE system?
A charging port would not have data lines connected.
Just a current limited 5V DC outlet with an USB Form A socket.
For a data connection attack vectors are very dependent on OS used and how well it is configured.
Windows has a thing for round heels in that respect. Even when the MCP says it is save.

Unixies like Linux, Android, Apple can be made save.