SQL injection, which exploits a vulnerability in the application's database query to execute malicious SQL commands.
Cross-site scripting (XSS), which injects malicious JavaScript code into the application's web page to execute on the client-side browser.
Directory traversal, which accesses files or directories outside of the intended scope by manipulating the file path.
In this case, the security engineer should recommend input validation as the best mitigation technique, because it would:
Prevent the exfiltration of a company report by validating the file parameter in the URL and ensuring that it matches a predefined list of allowed files or formats.
Enhance the security of the web application by filtering out any malicious or invalid input from users or attackers.
Be more effective and efficient than other techniques, such as firewall, WAF (Web Application Firewall), or DLP (Data Loss Prevention), which may not be able to detect or block all types of web application attacks.

The code snippet presents a buffer size risk where the user input (username) is accepted without limiting the number of characters, potentially leading to buffer overflow vulnerabilities. The best solution is to implement input validation that limits the input to a maximum of 20 characters, matching the buffer size defined in the code. This prevents overflow attacks by ensuring that user input does not exceed the allocated memory space.
Other options, like adding more parameters or allowing alphanumeric characters, do not directly address the root cause of buffer overflow vulnerabilities. CASP+ stresses the importance of proper input validation and bounds checking as critical security measures.
References:
* CASP+ CAS-004 Exam Objectives: Domain 2.0 - Enterprise Security Operations (Input Validation and Buffer Overflow Prevention)
* CompTIA CASP+ Study Guide: Secure Coding Practices and Input Validation Techniques

Email signatures provide non-repudiation, which ensures that the sender of an email cannot deny having sent it. A digital signature, when attached to an email, uses cryptographic techniques to verify the sender's identity and confirm the authenticity of the message. This feature helps establish trust by preventing tampering and ensuring the integrity of the communication. CASP+ emphasizes the role of digital signatures in ensuring non- repudiation in secure communication protocols.
References:
* CASP+ CAS-004 Exam Objectives: Domain 2.0 - Enterprise Security Operations (Non-repudiation and Digital Signatures)
* CompTIA CASP+ Study Guide: Email Security and Non-repudiation with Digital Signatures

For an organization transitioning its Wi-Fi to WPA2/WPA3 Enterprise with EAP-TLS, X.509 certificates are crucial. EAP-TLS (Extensible Authentication Protocol-Transport Layer Security) is a certificate-based authentication protocol, and for it to work, both the client and server must have valid X.509 certificates. This ensures that the mobile devices can authenticate themselves securely to the wireless network. Other options like IPSec configurations or TOTP tokens are not relevant in the context of EAP-TLS wireless authentication.
CASP+ highlights the importance of certificate management in secure wireless authentication protocols.
References:
* CASP+ CAS-004 Exam Objectives: Domain 3.0 - Enterprise Security Architecture (Wireless Authentication and EAP-TLS)
* CompTIA CASP+ Study Guide: Certificate Management for EAP-TLS