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PicoCTF 2019 - extensions

Author: PinkNoize

Forensics - 150

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

Writeup

This challenge provides us with a file called flag.txt. If we try to cat the file we get random garbage.

$ cat flag.txt 
�PNG
�
IHDR���^�sRGB���gAMA��
                      �a	pHYs

Near the top of the garbage, we see "PNG" this suggests that this may be a PNG file. We can check this with the file command.

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

This confirms that this really is a PNG file and the .txt extension really has no effect on the actual file structure. We can rename the file to flag.png and view for the flag.

The flag is picoCTF{now_you_know_about_extensions}.