Use unzip -l suspicious.epub or open in 7-Zip. A valid EPUB contains:
Some academic or industrial tools (e.g., OpenCV scripts, MATLAB video processing, or deprecated VideoAnalyzer) export metadata as EPUB for strange reasons—e.g., generating a “report” of motion tracking. 62 117 68 199 8055 Viewerframe Mode Motion.epub
Example:
Hackers can use an open camera as a gateway to access other devices on your home or business network. Use unzip -l suspicious