Author: Susie/Pandu
Matryoshka dolls are a set of wooden dolls of decreasing size placed one inside another. What's the final one? Image: this
Hint 1
Wait, you can hide files inside files? But how do you find them?Hint 2
Make sure to submit the flag as picoCTF{XXXXX}The picture has actually a hidden file which is another picture with a hidden file and so on. In total there are four pictures and the last one contains a hidden txt with the flag.
To extract the hidden files a command like unzip can be used.
If your editor shows Unicode replacement characters you can also use cat flag.txt to get the flag without them.
Show flag
picoCTF{ac0072c423ee13bfc0b166af72e25b61}