ᐅ Painting over moisture stains?

A room is going to be repainted. For the first time in 30 years, there are moisture stains. It is located on the east side of the building. The cause could be that the room door was often left open, allowing moisture from warmer rooms to condense on the walls due to air circulation.

See photo:

Should a special treatment be applied before painting with regular paint?

Thank you

Gerd53 schrieb:

The cause could be that the interior door was often left open, and with air circulation, moisture from warmer rooms condensed on the walls.

If the interior door is open, the room needs to be heated.
If it’s wallpaper, check for mold stains or even mold underneath.
Is it a corner with two exterior walls?

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

I would wash off the old paint and repaint with mold-resistant paint. Then, heat the room more effectively.

Nida35a schrieb:

I would wash off the old paint and repaint with a mold-resistant paint.
Then heat the room more warmly afterward.

I cleaned the wall with "vinegar water" and a household sponge. The vinegar concentration was very low, less than 1:100 ratio.
The stains are very easy to wash off (see photo). I changed the water several times and rinsed the sponge frequently. At the lower edge of the current plaster area, I immediately removed excess water with kitchen paper towels to avoid leaving a dirty line. This way, even larger surfaces are easy to clean.