This time I have read the description carefully :)
The main thing is that the hardwork I did for previous challenge for finding the ZIP file was not wasted LOL
So we don't have to do any bruteforce for finding the ZIP Password
Where to look for password?? I did filescan on that disk image to find if any important file where the zip password could be..but I couldn't find anything useful.
Then I thought of checking the web chats of the channel! so this time I just used strings on disk image and used grep to print only strings related to : FwordCTF{top_secret_channel} and BOOM! we got the zip password : fw0rdsecretp4ss Unlocked the ZIP and got the flag!!
