PicoCTF19 Extensions

Challenge

This is a really weird text file TXT? Can you find the flag?

Hints

How do operating systems know what kind of file it is? (It's not just the ending!

Make sure to submit the flag as picoCTF{XXXXX}

Solution

$ file flag.txt
flag.txt: PNG image data, 1697 x 608, 8-bit/color RGB, non-interlaced
$ cp flag.txt flag_extensions.png

Open the file and see the flag.

Flag

picoCTF{now_you_know_about_extensions}