The question about if an international organization is working for the interests of its members or their staff is a very tough one. The perceived intent of actions and the ever-present realist thinking that nations are working through whatever channels they can to get an advantage can make one think the international organizations are simply shells for the nations which make up the organizations. However, the massive bureaucracy of some international organizations give them sovereignty and authority over specific issue areas in international relations, which allow them to be free from influence of their member states.
The World Bank and the IMF are both governed by citizens of the nations which make the largest donations to each budget. This means that those that are the highest employees of the organizations, the ones charged with the overall direction and vision will be for their tenure. As well, because these are based in the nations or allies of the nations which are the largest donors, they end up hiring more people in that area. World Bank and IMF diversity reports show that a significant amount of those working in those institutions are from developed nations or have citizenship to one of the major donor nations. Because of this, it is reasonable to say that those working for the organization are acting on both what the member interests are and the staff because they are likely in line with one another. The Bretton Woods institutions are susceptible to their actions reflection the powerful member states due to their status and make up.
However, there are plenty of groups that do not have the power to change the makeup of nations and their financial choices, instead working in the areas of humanitarian relief and other less controversial area. The UN High Commission on Human Rights (UNCHR) and the UN Refugee Agency are particularly powerful actors but are charged to be apolitical. However, because these two groups are recognized as the leaders in the areas they are charged with caring for, they are able to work inside of states without many questioning their legitimacy to do so. They because they are tasked and are working to alleviate specific issues, it is not the member nations which donate money, goods, and other resources that have power over the choices, the staff of the agency is able to circumvent nations.
This is shown in a new probe the UNHCR is making inquiring if Israel committed war crimes in Gaza in its most recent campaign. With the close partnership the United States has with Israel, this would not be a popular action, especially with the weight the US has in the UN. Therefore, we can see that UNHCR is working independently is not facing significant flack for making this choice (although possibly overshadowed by actions in Syria). This shows when an organization is given the authority and sovereignty over an issue, they will take action by their staffs’ choice even if the choice is against the wants of a state with power and influence in the organization.