I was changing tyres just now and since the current car (VW Caddy) it a bit longer than the old one I had to turn it around once to change the front wheels. Not paying attention at that moment, when I went backwards, the jack was still up with one rear wheel.
I guess the suspension didn't mind that much, but the jack scraped along the attachment point and removed a bit of the black (or paint colour, apparently) and grey rubbery material (which I guess is corrosion protection) there:
As far as I can tell that's not immediately metal underneath there, though I'm not quite sure what it is.
On a scale from »repair immediately« to »since it's no longer winter it can probably remain like that for a week without further damage« how bad is this?