Based on the question and discussion, the AI agrees with the suggested answer, which is D. SCA.
SCA (Software Composition Analysis) tools are specifically designed to identify the presence of vulnerable open-source libraries within an application. They achieve this by analyzing the application's dependencies, checking for known security vulnerabilities, and providing insights into outdated or vulnerable components.
Here's a detailed breakdown:

Why SCA is the best choice: SCA tools excel at identifying vulnerabilities in third-party libraries. They maintain databases of known vulnerabilities (e.g., from the National Vulnerability Database - NVD) and compare the libraries used in the application against these databases. This allows them to flag components with known security issues, such as those listed in CVE (Common Vulnerabilities and Exposures) records.
Why other options are incorrect:
- A. VM (Vulnerability Management): Vulnerability management tools are broader in scope. They focus on identifying, classifying, remediating, and mitigating vulnerabilities in various IT assets, including operating systems, network devices, and applications. While they might identify some vulnerable open-source components, they are not specialized for this task.
- B. IAST (Interactive Application Security Testing): IAST tools are designed to identify security vulnerabilities in an application while it's running, typically in a testing or QA environment. They instrument the application and monitor its behavior to detect issues like SQL injection or cross-site scripting. IAST is more focused on detecting security flaws in the application's own code rather than identifying vulnerable open-source libraries.
- C. DAST (Dynamic Application Security Testing): DAST tools test an application from the outside, without access to its source code. They simulate real-world attacks to identify vulnerabilities. While DAST can uncover some issues related to vulnerable libraries (e.g., if a library exposes a vulnerable endpoint), it is not the primary method for identifying vulnerable open-source components. DAST tools typically do not specialize in identifying issues within open-source libraries.

Therefore, for the purpose of identifying vulnerable open-source libraries, SCA is the most appropriate tool.

Reasoning Details: The primary goal of a penetration tester in this scenario is to find vulnerable open-source libraries. SCA tools are specifically built for this task, offering features like dependency analysis, vulnerability database integration, and reporting on outdated components.

In summary, the penetration tester should leverage SCA tools to efficiently and accurately identify vulnerable open-source libraries in the web application.

Citations:

OWASP Software Component Analysis, https://owasp.org/www-project-software-component-analysis/
Snyk SCA, https://snyk.io/product/software-composition-analysis/