Ох уж этот кладмен (Oh, this stash guy)

cyberareactf

Task: a DOCX access-control migration report hides a flag with no standard stego vector (no macros, embeddings, or hidden text). Solution: a customXml part reveals an arithmetic rule M = B + L + K; the hidden channel is OOXML bookmark names NB_<seq>_<M> around English labels, decoded as B = M - len(label) - key_digit(Request ID 23063).