Upon running the binary you are prompted to enter password. You may find it laying down in disassembly. iirc it's `kaiokenx20`.  Then it's asks which "application" to show you. If you select `7` ("Flag") it exits with `Not enough permissions` message.  Attack vector is buffer overflow of password as memory for filename is right next to it.  One small thing is strlen check for length of filename so you can't just throw `flag.txt` inside. Required length is 36 symbols, so you may pad your filename with `./`.  Final overflow would be `kaiokenx20AAAAAA././././././././././././././././flag.txt`.