I only know about the A300 but I think the later ones have similar operation.
If the door is opened from outside with the slide armed the mechanical linkage in the door will dis-arm the slide so there is no chance of the slide deploying.
However it is normally the cabin crew who open the door and if they have not dis-armed it, the slide will deploy and this is where the danger lies. It is very rare and procedures should prevent it happening, but I've seen it twice in my career.
Hope this helps.