One problem related to coolant leaking has been reported for the 2015 Subaru Forester. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2015 Subaru Forester based on all problems reported for the 2015 Forester.
I have had my Forester since Nov 2014, and during the time of owning the vehicle I have had to add a quart of oil roughly every 2500-3000 miles in between services (5000 mile service interval) as the check engine oil level light illuminates. At two points that I have had the vehicle (roughly 50000 and 80000), I have had oil consumption tests run on the vehicle, both were returned as normal, and that the amount of oil consumed by the engine was within the parameters of the design. On 24 may 2019, I turned the vehicle in to a Subaru dealership in hawaii for servicing (have used this location in the past), and they informed me that the oil is leaking into the coolant system inside the engine, and that the engine needs to be pulled and the upper oil pan seals and head gaskets need to be replaced. I fail to understand how this issue could go undiagnosed for the entirety that I have been having the vehicle serviced at Subaru dealerships, through two oil consumption tests, and just now the issue was diagnosed. I also understand that the amount of oil missing from the pan might not have been "consumed" as the service technician made a point to state, but I would say a pretty good indicator of an issue with the oil system, is the system losing oil. Also, after a cursory search of internet forums, this issue seems to be a common trend among Subaru Foresters, and the symptoms were covered in a similar technical service bulletin (TSB no. 02-157-14r), which includes my year, make, and model, but differs in that it only covers the manual transmission cars, not vehicles equipped with the cvt.