As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ONT - AIR TURN BACK - AFTER DEPARTURE CREW REPORTED THE LT FORWARD OVER WING EMERGENCY EXIT OPEN ON ECAM. NO PRESSURIZATION PROBLEMS WERE REPORTED AND NO EMERGENCY WAS DECLARED. CREW RETURNED TO ONT AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE REMOVED AND RE-SEATED THE LEFT FORWARD OVERWING EMERGENCY EXIT HANDLE, MESSAGE CLEARED.