The "source" suffix in the filename might imply that a specific frame contains the key.
VLC (using ‘e’ to advance frame-by-frame) or FFmpeg . 0h8q1ak2acptoechqhoxq_source.mp4
In many instances of this specific file being discussed in security circles, the solution involves or discovering a hidden data stream using ffprobe that isn't rendered by standard video players. The "source" suffix in the filename might imply
Look for single-frame flashes, QR codes hidden in high-contrast areas, or "ghost" text that only appears for 1/60th of a second. QR codes hidden in high-contrast areas
strings 0h8q1ak2acptoechqhoxq_source.mp4 | grep -i "CTF" (or the specific tag for the competition).