Zipper
In this challenge, we have access to this zip. First I tried to unzip it and we find a PDF with two images talking about the zip format. I tried to run binwalk on them with no luck. But after a wile, I tried to run it on the zip itself:
As we can see, we have the zip containing the folder whatiszip, a bunch of other zip or zlib files but also a PNG image. We use binwalk to extract it but the classic -e won’t work. In this case, we use the --dd=.* option to recover every files.
And the PNG image gives us the flag:
