A member of staff may put in a special sealed bag any products that you have acquired from a duty-free shop or during a flight plus the receipts. Permission to board the flight will be given after this bag and the associated receipts have been checked at the security point.
If your journey involves connecting flights, it is very important that you do not open any special duty-free shopping bags acquired at shops or on flights until you reach your final destination airport. Otherwise the contents of the bag may be confiscated at a transfer airport.
If you have any doubts on this matter, please enquire at the airline or travel agent before your journey. You are obliged to cooperate with the security staff and airline personnel at the airport.