Negative testing is an example of the type of testing that the security team performed on the organization’s customer service portal. Negative testing is a technique that tests the system or the application with invalid, unexpected, or erroneous inputs or data, such as alphabets in a numeric field, special characters in a text field, or null values in a mandatory field. Negative testing can help to evaluate the robustness, stability, and error handling of the system or the application, and to identify and fix the bugs, flaws, or vulnerabilities that may cause the system or the application to crash, malfunction, or behave unpredictably. The other options are not examples of the type of testing that the security team performed on the organization’s customer service portal, as they either do not involve invalid, unexpected, or erroneous inputs or data, or do not match the outcome of the testing. References: CISSP - Certified Information Systems Security Professional, Domain 8. Software Development Security, 8.2 Understand and apply security in the software development life cycle, 8.2.2 Assess the effectiveness of software security, 8.2.2.1 Testing methods; CISSP Exam Outline, Domain 8. Software Development Security, 8.2 Understand and apply security in the software development life cycle, 8.2.2 Assess the effectiveness of software security, 8.2.2.1 Testing methods