In this context, "filthy" likely refers to one of two things: moral transgression or actual domestic conflict.
The use of a file extension like .mp4 in a title serves a specific rhetorical purpose: very filthy step Mommy video.mp4
: The mother figure is traditionally seen as a provider of safety. By adding "step" and "filthy," the title immediately signals a subversion of that safety, playing on the fear of an intruder within the domestic sphere. In this context, "filthy" likely refers to one