[DangeloInspections]

Wow....that is strange and unique. So...the best way to start looking into this is to try to determine if it is moisture intrusion or not. It appears to be.

So....assuming it is....is it coming from the slab, or is it coming from the wall? Is there any pipes in that adjacent wall? Is that wall drywall or block? Any water pipes or vent pipes? What is above the wall? On some models the top of this wall may be where the roof hits against the front entry wall.

My guess is that the water (if it is a leak, etc) is coming from above.....either from a pipe or from a breach in the roof or flashing.

Does it dry out or get worse after a rain? Is there laundry on the other side? Does putting a fan overnight on this change the appearance at all?

Of course it is difficult to speculate with just one picture. I'm just trying to help by asking some questions. Of course, it could be a leak or I've even seen concrete be different shades with no problem at all......although this does look like it may be as you suspect. Hope this helps! Moisture meters and Thermal imaging cameras may tell us more.

Respectfully,

Frank