Hackers target United Nations networks

Hackers compromised the UN's networks, affecting 33 servers in Geneva and 4 in Vienna. They exploited a flaw in Microsoft's SharePoint, exfiltrating 400GB of data, including internal documents and staff records. Despite the breach, staff were only asked to change passwords without being informed of the incident.

What software flaw was exploited by the hackers to infiltrate the United Nations networks?

What action was taken by staff members following the breach?