As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED. L4 LAVATORY SMOKE ALERT IN FLIGHT WITH CORRESPONDING ECAM WARNING FOR A DURATION OF 3 SECONDS FLIGHT ATTENDANT CONFIRMED NO SMELL OR VISUAL OF SMOKE. MAINTENANCE REPLACED AFT LEFT HAND LAVATORY (L4) SMOKE DETECTOR (4WQ) PER AMM 26-17-15 PB 0401. ACCOMPLISHED SATISFACTORY OPERATIONAL CHECK.