Water under carpet in the front.
Could be a few things. One thing to check first is that your sunroof drains are clear. If you have one. Here’s how to do it.
Is it antifreeze? Could be heater core. Does your windshield fog up when you turn defrosters on?
Toyota released a redesigned rear hatch seal, also some people were getting water from the rear A/C units clogged condensation drain.
Siennas floor pan is a bit lower in the front so water will pool up front no matter where the leak is. I had water pooling up front from a rear hatch leak.