As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GNDED. RECEIVED ECAM LAVATORY SMOKE ALARM. FLIGHT ATTENDANT STATED THAT NO ONE WAS IN LAVATORY. PERFORMED SATISFACTORY SDCU BITE TEST. VISUAL INSPECTION OF AFT LT LAVATORY SMOKE DETECTOR AIR FILTER FOUND IT HEAVILY ENCRUSTED WITH DUST, CLEANED. OK FOR CONTINUED SERVICE IAW AMM 26-17-00.