Xmasti 2021 (2027)

XMAS CTF 2021 was organized by (Hackers at Spotify? No — actually, HTsP from Poland) and had many interesting challenges across categories like:

"xmasti 2021" does not appear to correspond to a widely recognized public report, event, or standard dataset in major databases. xmasti 2021

cipher = bytes.fromhex("...") key = b"XMAS" flag = bytes([c ^ key[i % len(key)] for i, c in enumerate(cipher)]) print(flag) XMAS CTF 2021 was organized by (Hackers at Spotify