I downloaded the file given to me and opened it in a text editor, and it showed a flag immediately:

flag{ab3cbaf45def9056dbfad706d597fb53}

I was certain this is some kind of decoy flag, but it was accepted when I provided it.

Also, you can learn on Google what cat does. It prints out the content of a given file.

Obviously, this was just warm-up. I don't think was exactly a security issue, but it was good to get my mind on opening the Linux VM.