The WRX STI has been assigned 107 TSBs over 2 model years.
TSBs contain recommended steps and procedures for diagnosing or repairing a known problem. They are issued directly by Subaru to service technicians. You'll often see TSBs used as evidence in lawsuits when owners feel the automaker should help with repairs.
A TSB can cover multiple models and years. The 2015 WRX STI has been involved in the most campaigns with 94 total service bulletins.
TSB Counts by Model Year
Clicking on a model year will bring you to CarComplaints.com which has a full list of documents from the NHTSA.