Yellow stuff inside PVC windows.

virginblue4

Hi all, I’ve just noticed that the internal window boards and reveals seem to be stained with yellow splashes. Looking closer, there seems to be some yellow stuff coming out of a small crack and maybe that’s what has been seeping down. What on earth is it? Is it some sort of mould, or maybe water penetration mixing with some sort of hidden rust? There is a concrete lintel above the window. 

thebullsback

my guess will be the expanding foam many people use is breaking down due to water ingres 

markin

Looks like you have water leaking in, check the outside silicone, and pointing.