It'a a classic restricted shell jail task. Connect to the console, and execute

> rbash-5.0$ echo *
>
> flag-xEpAN7X3tGYjt4Y0p0FD.txt jail.sh

No way to execute basic command like cat, ls:
rbash: cat: command not found

But we can to this trick


Note: in bash < is stdin redirect, backticks used for executing command and use output of command as arguments data