As the article says, passenger jet aircraft are always pressurised. The pressurisation comes in just after take-off and only cuts out just before landing. So as the aircraft climbs to its cruising height of 35,000 - 40,000 ft, the cabin "climbs" to 6,000 - 8,000 ft, gradually achieving a differential pressure about 8.5 lbs psi.
Having a door/window come open below 10,000 ft is most unlikely. For one thing they are nearly all "plug" fittings and have to be pulled inwards to open. Just picture the square inches in a window panel and multiply them by 8.5. That's the force needed to open them in pressurised flight. They could come open below 10,000 feet, I suppose. There would still be a depressurisation, but less violent, since the differential pressure is less, and those on board could breathe without oxygen at those heights. People/things could still be blown (not sucked) out, even when the inside pressure is reduced to the same as outside, just as if you open a car window at 70 mph you can lose your newspaper! And relax. You are in the hands of professional pilots who know how to deal with things like this. I know - I used to be one. I never had a decompression, but I practised the drill regularly in the flight simulator.