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INSERT_CHALLENGE_TITLE_HERE

Challenge​

Imported from local notes.md.

Solution​

Original Notes​

INSERT_CHALLENGE_TITLE_HERE

Challenge Summary​

  • Given: a single JPEG attachment named flag.jpg and a short placeholder description with a provided SHA1 hash.
  • Goal: recover the hidden flag in the format CIT{...}.
  • Constraints: no remote endpoint or password is involved; the solve is entirely local to the image file.

Initial Recon / Triage​

  • Observations: the image itself only contains the visible placeholder text [INSERT A HIDDEN MESSAGE OR SOMETHING..], which strongly suggests a metadata or simple stego warm-up rather than a complex visual puzzle.
  • File identification: flag.jpg is a normal JPEG/JFIF file with embedded EXIF metadata.
  • Entry points: verify the provided SHA1, inspect EXIF tags, and scan for obvious embedded strings.

Hypotheses & Approach​

  • Hypothesis 1: the image hash in the prompt is just an integrity check for the provided file.
  • Hypothesis 2: because the challenge is a low-solve-count warm-up stego prompt, the flag is likely stored directly in JPEG metadata.

Execution Steps (Reproducible)​

Stage 1​

Commands:

cd /root/cit2026CTF/INSERT_CHALLENGE_TITLE_HERE
sha1sum starting_files/flag.jpg
file starting_files/flag.jpg
exiftool starting_files/flag.jpg

Results:

  • The SHA1 matched the prompt exactly: 1cdc80f8c797645b9d92e34a4c6c09022e5378aa.
  • exiftool revealed an Image Description EXIF tag containing the flag directly.

Stage 2​

Commands:

cd /root/cit2026CTF/INSERT_CHALLENGE_TITLE_HERE
strings -a -n 6 starting_files/flag.jpg | grep 'CIT{'

Results:

  • The same flag string appears in the JPEG data stream as a printable string, which confirms the EXIF finding.
  • The recovered flag is CIT{ur_w4rm1ng_up_n0w}.

Artifacts Produced​

  • No extra extraction script was needed; the solve is fully reproducible with the commands above.

Flag​

CIT{ur_w4rm1ng_up_n0w}