Dave Divecha

I dont want to say I know the answer as I just purchased my Highlander,but my past experience with vehicles and water is that there is often a drain hole and or vent in the light assembly, it sometimes has a rubber tube attached to it and if it gets clogged (even a small amount of dirt could do this) it will allow water to collect. It is also possible that the plastic lens is cracked or the seam between the lens and the housing has separated. It only takes a small crack to let water in especially with the amount of rain we have had in VA lately. If you remove the taillight and clean it and carefully blow some compressed air into anything that looks like a drain or vent and then inspect for any cracks, maybe, hopefully you will find the answer. Hope that helps