Enhance Mobile Video Indexing with "videohindexnxxcommobile"

# unzip and read extra file subprocess.run(["unzip", "-o", "payload.zip", "-d", "zip_contents"], check=True) with open("zip_contents/secret.txt") as f: print("[+] Zip flag :", f.read().strip()) Running it yields the flag instantly. | Technique | Why it mattered | |-----------|-----------------| | Manifest inspection | Revealed the hard‑coded download URL. | | Static smali review | Confirmed that the URL is not obfuscated and that the file is stored locally. | | Dynamic pulling of internal files ( run-as ) | Allowed us to retrieve the binary blob without needing root. | | Magic‑byte hunting ( file , strings ) | Exposed that the blob is a concatenation of two formats. | | Binary splitting (dd) | Required to separate the video from the zip. | | Multimedia forensics (ffmpeg, QR decode, audio extraction) | Gave three independent flag locations – a classic “defense‑in‑depth” style CTF. | | Automation | A short script can solve the challenge end‑to‑end, useful for time‑pressured CTFs. | 10. Final Flag flagv1d30_h1dd3n_1n_0bfu5c473 (Any of the three copies – QR, audio, or secret.txt – is accepted.) End of write‑up.

Take a screenshot (or extract a frame):

# convert video subprocess.run(["ffmpeg", "-y", "-i", "video.h264", "-c", "copy", "video.mp4"], check=True) subprocess.run(["ffmpeg", "-y", "-i", "video.mp4", "-vf", "select=eq(n\\,10)", "-vframes", "1", "frame.png"], check=True)