It seems searching on the forum brings up a few posts and most lead to the rear wiper pipe disconnecting hence a puddle... Your rear washer still working?
If not maybe check the seal with someone on the inside with the seats down and you hosing water over the rear end... You look for air bubbles and the inside person looks for a leak...
My conclusion of random posts on here lol
Cheers
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Currently Driving - SEAT
Leon Mk2 Cupra R 2010
Previous Car - SEAT
Leon Mk2 FR 2007