u/FabienJ88

Hi everybody! As you can see, a leak has been ongoing in parts of my wall and ceiling for several months now. It took me ages to notice the small stain on wall that was very slowly growing. It's in the process of being fixed: the building heating system is probably at fault here according to my landlady’s plumber.
I'm worried about what I found under some paint that fell off from the ceiling. Could it be mold? It's dry to the touch, but I know that doesn't mean it's not dangerous. 

--