What was found
THE AIRCRAFT WAS NOT GROUNDED. ON DESCENT INTO CUN AT APPROXIMATELY 90000FT. FLIGHT ATTENDANTS CALLED TO REPORT FUME EVENT IN AFT AND MID CABIN (ROWS 9-34). FLIGHT DECK ALSO HAD SOME SMELL COMPLIED WITH QRH SMOKE/AVIONICS SMOKE FUMES PROCEDURE.FUMES SEEMED TO CLEAR ON APPROACH. ACCOMPLISHED T/S CABIN AIR QUALITY INSPECTION AND CHECK PER J/C 26L00021001, FOUND YELLOW HYD SYSTEM RESERVIOR OVER-SERVICED , DRAIN YELLOW AND RESERVICED PER AMM 12-12-29. NO OTHER FAULTS NOTED. OK FOR SERVICE.