Worrying lapse in airport security

I WOULD like to highlight what appears to be a lapse in security at KLIA. I was initially impressed by the thorough security patting-down of all passengers through gate H10 when I prepared to board MH619 on July 7 to Singapore.

But I was shocked when I entered the holding area and saw another door which was wide open and people were just trotting in and out without undergoing any security check. When I asked about this, I was told that they were passengers on a domestic flight to Penang and no further security check was required. This is shocking because passengers for both flights were sharing the same common holding area!