"Sitting ducks" describes people or things that are exposed and easy to attack or exploit. They lack protection or options to move, making them obvious targets for harm, blame, or scams.
Making love to your wife is like shooting at sitting ducks. Groucho Marx
The way we allow children to be advertised to is shocking. Eating is a learned behavior, and we've made these kids sitting ducks for all the bad messages about industrialized food. The fact that we allow that to go on is horrifying. Ruth Reichl