A vulnerability assessment is a process of identifying and evaluating the weaknesses or gaps in an application that may expose it to potential threats or attacks.
When vulnerability assessment results identify a weakness in an application, the first thing that a risk practitioner should do is to assess the risk to determine mitigation needed. This means that the risk practitioner should analyze the likelihood and impact of the weakness being exploited, the existing controls that are in place to prevent or reduce the exploitation, and the residual risk that remains after applying the controls.
Assessing the risk to determine mitigation needed helps to prioritize the actions that are required to address the weakness, such as implementing new or additional controls, accepting the risk, transferring the risk, or avoiding the risk.
The other options are not the first things that a risk practitioner should do when vulnerability assessment results identify a weakness in an application. They are either secondary or not essential for risk management.
The references for this answer are:
Risk IT Framework, page 18
Information Technology & Security, page 12
Risk Scenarios Starter Pack, page 10
