unrar et strings
dobre
I found it easy. If you have done all the "EASY" forensics problems, this one should be a breeze
For who doesn't understand binwalk, strings and grep like me.. try to make the jpeg as zip file (using .zip extension) then using online zip extractor(https://www.ezyzip.com/unzip-files-online.html), open the zip file.. there you can see folder & then select b.jpg.. then save the jpg and use cyberchef (Pro tip: Use strings as extractor).. You know to use cyberchef right?
at strings i've got only "This is not the flag you are looking for". Binwalk didn't find any hidden file.
4 days ago
use binwalk [binwalk itself must be run as root i.e (--run-as=root), then extract the zip file, locate extracted file there you'll see "b.jpg", use strings ie "strings b.jpg", flag waits you. have a goodday :)