Don't know why it leaked, but it hasn't anymore - only about twice, the first time a little bit (don't know the date), the second time there was quite a bit of water in the trunk, had to open the drain cap in the bottom in trunk. Plus use a small shop vac to vacuum it out.

This problem was due to a crack in the fire wall beneath the front windshield. It cause mold, and mildew under the carpet on the passenger side. I did the remediation myself to save money but it was a real pain to do.