What could cause these spots?

[JCGD]

Hi, in our ensuite bathroom we have these spots in the wall (exterior - cavity wall). Any idea what could cause these spots?

 

[23vc]

Looks like spots of mould caused by condensation, where hot steamy air hits the cold wall. Does extractor fan work? Is wall insulated?

 

[JCGD]

Would need to double check extractor. The walls are filled with the blown fibre stuff.

I noticed the waste pipes on the exterior are not sealed around the pipes, is it possible that the cavity would get wet from this?

 

[23vc]

It’s not coming through the wall, more that the surface of the wall is cold which combined with bad extraction would cause what you’re seeing