The problem with film paper is that it impedes the breathability of the materials. If your house is a lot more humid than the author's house, unpacking the painting will result in the cardboard absorbing a lot of water (and contaminants). However, whatever contaminants currently invest the cardboard will prosper in their hermetically sealed vivarium, and affect the cardboard - as well as the paint.
If the work is made with acrylics, it probably has had enough time to dry sufficiently, and can suffer low breathability for a while. But if it's oil paint, you really don't want to keep the artwork sealed in film, as it will impede the drying process and likely cause long-term problems.
I'd suggest letting a friend, family member, neighbour, colleague, or acquaintance (I think those are all the options :-) ), store it in a space where - as Elmy suggests in the comments - the atmosphere is stable.
You'll want low humidity, a temperature between ca. 15° and 25° Celsius (59° and 77° Fahrenheit), low light or darkness, no dust, and to keep it away from doors, windows, or other potential sources of shifts in these conditions, and out of reach of most things: you don't want people storing things on top of it, or against it, or for it to keep getting moved.
If that's really not an option, storing it in the most environmentally stable room of your house is the best choice, preferably - as fixer1234 suggests - along with a dehumidifier.
But I would advise you to take the work out of the film in that case and wrap it - loosely! - in bubble wrap: this both allows for breathing and will protect the work, especially the edges. Then place it in another container, like a drawer, where it will stay out of the light and have an extra layer of isolation, so that any changes in temperature and humidity will be minimized.