Paint over moisture stains?

A room is to be repainted. It has moisture stains for the first time in 30 years. It is located on the east side of the building. The cause could be that the room door was often open and moisture from warmer rooms settled on the walls due to air circulation.

See photo:

Should a special measure be carried out before painting with a commercially available paint?

Thank you

The cause could be that the room door was often open and moisture from warmer rooms condensed on the walls due to air circulation.

if the room door is open, the room must be heated. If it is wallpaper, then check if there are mold stains or already mold underneath. Is it a corner with two exterior walls?

The room is painted with a standard paint from the hardware store. The affected area is the exterior wall and, to a small extent, the adjoining walls near the exterior wall. It does not appear to be mold. There are many small individual spots. They are brownish.

I would wash off the old paint and repaint with mold-resistant paint. And then heat the room warmer.

I would wash off the old paint and repaint with mold-resistant paint. And then heat the room warmer

Thank you!

I cleaned the wall with "vinegar water" and a household sponge. There was very little vinegar, in a ratio of less than 1:100. The stains are very easy to wash off (see photo). I changed the water several times and rinsed the sponge often. At the lower edge of the current plaster area, I immediately removed excess water with kitchen paper, otherwise there would have been a dirt line. This way, larger areas are also easy to clean.