As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PHL - FL 98 - ENROUTE, THE L1 WINDOW OUTER PANE SHATTERED. NO PRESSURIZATION LOSS OCCURRED, HOWEVER THE CAPTAIN COULD NOT SEE OUT THE WINDOW. FLIGHT RETURNED TO PHL AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE REPLACED THE L1 WINDOW.