Strange orange mold behind skirting board

ashe

Partner just pointed out a strange yellow/orange stuff that keeps coming out of the skirting board gap between the skirting and tile. 

I prized the skirting off and there was a few blobs of it, it looked like expanding foam but gloopy in parts and brittle in others 

ive googled it and found two images that look just like what I've found;

the first image is a Twitter image where someone has a waste leak in their room 

the second image is a toilet and the comments suggest it's a wax seal 

this skirting is right under a radiator valve where we had a dripping leak fixed a few months back. It also backs onto a boxed in waste stack, so it doesn't seem like it should be wax seal, so am worried it's a waste leak but no bad smell. The wall behind skirting did feel mildly damp and the tile adhesive under it was darker so looked like could have been done trapped moisture- We've left it off for the time being to see if it dries out and monitor it but curious if anyones experienced anything like it?


This is the corner where it was, in the gap between floor tile and skirting middle-right, the blurred thing at the top is the rad pipe (which is dry), the wall on the last hand side is the boxing in from the waste stack which runs down from bathroom into our hallway

Close up of that area:

The below two pics are the ones I found online with identical appearance 

shiraz99

It's a fungus, rather than a mold, though technically speaking mold is just another type of fungi. Just treat it with a strong bleach solution to kill it off.

GDB2222

Has it dried out, or is the waste stack leaking? That fungus looks rather healthy to me, so there may still be moisture.