Knowing if it was on a social media thread, a specific website, or an old hard drive would help in identifying the exact content.
If you downloaded the file from an unknown site, run it through a security scan before opening. 80499.mp4
If this is related to a specific niche community (like an ARG or a specific gaming clip), it hasn't reached broader Wikipedia-level documentation . Technical Context of .MP4 Files Knowing if it was on a social media