Water began to leak into the cabin via the B-pillars when it rained. Happened more frequently on drivers side than passengers side. Also leaked into the cabin on the tailgate pillars, but just once. Took it to the dealer, and they initially stated the sunroof drains would need to be replaced. After the sunroof drains were replaced, the problem persisted. Took it back to the dealer where upon further inspection it was determined there were cracks in the roof rails and it allowed water to enter the cabin. No charge for that, since their initial recommendation had not remedied the issue. Problem has been resolved ever since.

Update from May 18, 2020: Roof started leaking yet again. Took the car to my family mechanic who diagnosed it being the roof rails, which continue to crack. I had the base of the roof rails sealed and bonded, and the problem went away: but not before costing $300 to fix (on top of the $700 the dealer charged me the first time around). PLEASE, if you are thinking of buying an 2007-2012 MDX, DO NOT BUY ONE WITH ROOF RAILS. I have spent over $1,000 on this problem ALONE (out of several) and I just pray the leaking will stop.