As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT ATTENDANTS REPORT EXTREMELY FOUL ODOR IN BACK OF AIRCRAFT. UNABLE TO LOCATE SOURCE <[01]. VERIFIED FLOW OF AFT SILL DRAINS PER AMM 38-31-06. REMOVED BOTH AFT LAV SHROUDS PER AMM 38-32-01. APPEARANCE DEPARTMENT CLEANED SHROUDS PER SIP. REINSTALLED BOTH AFT LAV SHROUDS PER AMM 38-32-01. NO SMELLS NOTED.