One of Santa's elf found this image of shiny bubbles. They are hiding a deep secret that you just have to "print" out.
There is a shiny_bubbles.png image inside, but you cannot extract it right away -- the archive is password-protected. One direct way to approach this is to brute-force the password, using fcrackzip tool and a decent word list. rockyou.txt is one such good enough and famous wordlist.
Bruteforcing the password:
$ fcrackzip -u -v -D -p rockyou.txt shiny_bubbles.zip
found file 'shiny_bubbles.png', (size cp/uc 1943050/2210609, flags 1, chk d877)
PASSWORD FOUND!!!!: pw == 4everspunkybubbles
Extract image from the archive:
Nothing unusual in the image itself, so let's look at the bytes. Quick hit - let's grep for ctf which is our flag format:
$ strings shiny_bubbles.png | grep ctf
1/1ctf{Wrong_Flag_Keep_Searching}PK
10/10ctf{Wrong_Flag_Keep_Searching}PK
100/100ctf{Wrong_Flag_Keep_Searching}PK
101/101ctf{Wrong_Flag_Keep_Searching}PK
102/102ctf{Wrong_Flag_Keep_Searching}PK
103/103ctf{Wrong_Flag_Keep_Searching}PK
104/104ctf{Wrong_Flag_Keep_Searching}PK
...
Okay, we're on a good path. Let's filter out "Wrong":
$ strings shiny_bubbles.png | grep ctf | grep -v Wrong
718/718ctf{th1s_I5_fuN_GREP_r0ck5}