What type of tool should Alex use to test for format string vulnerabilities in web applications?

Using a fuzzer is the most suitable approach for testing format string vulnerabilities in web applications. Fuzzing is a technique where random or unexpected input data is sent to a program to discover security vulnerabilities, including those related to format strings. Format string vulnerabilities occur when user input is incorrectly handled by the application, leading to potential memory corruption or information leakage.

Fuzzers can automate the process of generating inputs that can exploit weaknesses in how a program processes format strings. They systematically send various inputs to the target application and observe how it responds, thereby pinpointing any vulnerabilities that may exist. This approach can be particularly effective for web applications, which often handle numerous inputs from users in different formats.

Other tools, while useful in their own right, do not focus specifically on this type of vulnerability in the same effective manner as fuzzers. For instance, black box testing assesses the application without knowledge of its internal workings but does not actively test for specific vulnerabilities like a fuzzer does. Brute-force tools mainly try to crack passwords or encryption rather than identify vulnerabilities. Static analysis tools inspect source code for potential vulnerabilities, but they may not effectively detect runtime issues such as format string vulnerabilities that can manifest only during program execution. Therefore, the use of a fuzzer is