Moved into a new house and the bathroom has a foul odour and i suspect it has something to do with he black stuff all over the place. Could it be mold?
I am pretty sure that is mold. I would start with a bleach solution to clean it up. Rental? If so, I would have the landlord look at it and get it taken care of. Cleaning, painting with Kilz or Bullseye or something similar. Then monitor it for a few months.
That is black mold.
If you are renting, your landlord is most likely responsible for this - as it is a health hazard.
It can be cleaned with common household cleaners, like Tilex or Mildex, but you will want to do it in sections, if you don't plan to leave.
You should ventilate the area, and protect yourself, from the toxic fumes, produced by the chemicals.
Regular cleaning, will need to be done, to keep it from coming back - just not with the strong stuff.