Catering
Having just retired after many years in the business I always felt that whilst passenger bags were screened and accounted for, most flights travelled with unaccompanied baggage namely catering boxes and carts.
On short turnarounds they are lifted from the hold into a high lift truck and on longer turnarounds from the off airport catering facility.
One wonders how efficient the security screening is at somewhere like Sharm.
A small explosive in the rear galley would be catastrophic.