What's this happening near this radiator? (Pic attached)

[grazerl]

Hello. I noticed this in my mum's house, seems to have happened overnight. The liquid is water, and closer to the radiator leg a thick, oily substance. It seems to have melted the wooden circle under it 😲

What is happening here please?

Looks like leak to me.

Indeed

Water leak.
It's affected the filler used to hide the gap around the pipe where it goes through the floor. May just need the connection tightened up or redone, or it may need a new valve, or even a new radiator. It depends where the leak is.
Call a plumber.

Thank you! Plumber called.