3137.mp4 May 2026

If you found something in a single frame, explain how you extracted it using ffmpeg -i 3137.mp4 -vf "select=eq(n\,3137)" -vframes 1 out.png .

List your toolkit, such as ExifTool , FFmpeg , StegSolve , Sonic Visualizer , or Strings . 2. Initial Analysis Describe your first steps after receiving the file:

Did you find the flag by running strings 3137.mp4 | grep "CTF{" ? 4. Final Flag Flag: FLAGexample_flag_123 3137.mp4

This is the core of your write-up. Explain the "Aha!" moment:

A quick summary of the trick (e.g., "The flag was hidden in the LSB of the audio channel"). If you found something in a single frame,

Use file 3137.mp4 to confirm it is actually an MP4 and not a renamed archive or polyglot file.

If the video looked normal, did you check the audio track? Mention if you used Audacity or Sonic Visualizer to look at the Spectrogram for hidden text. Initial Analysis Describe your first steps after receiving

Did you run exiftool 3137.mp4 ? Often, flags or hints are hidden in the "Comment" or "Artist" tags.