Most tech-savvy investigators on YouTube's horror community categorize this as a "Digital Arg" (Alternate Reality Game) or a simple corrupted upload. The double extension is a common trope used to make a file look more "disturbing" or amateur, mimicking the way real leaked surveillance footage might be saved.
Users on Reddit's r/LostMedia have noted that the file often carries a heavy "mosquito" buzz or low-frequency humming that increases in volume until the file ends. tagaunfinished.mp4.mp4
Reports describe the video as containing distorted CCTV-style footage or handheld camera work of a rural area in the Philippines. It often features a figure standing in the distance before the video glitches into a digital freeze-frame. tagaunfinished.mp4.mp4