The CEH Web Application Security module explains that race conditions occur when systems improperly handle simultaneous requests, leading to unexpected behavior. In token-based authentication systems, poor synchronization between token expiration checks and validation logic can allow attackers to exploit timing gaps.
The observed pattern-failed attempts with expired tokens followed by successful access-suggests the attacker exploited a race condition where the application inconsistently validated token state.
Option C is correct.
Option A would not involve expired tokens.
Option B is highly impractical given secure token entropy.
Option D typically succeeds without repeated failures.
CEH highlights race conditions as subtle but dangerous logic flaws.

CEH v13 emphasizes that advanced injection attacks often evade input validation through encoding and obfuscation. A Web Application Firewall (WAF) with evasion detection can analyze request patterns, payload behavior, and anomalies in real time.
Code reviews are important but reactive. SIEM correlates logs after attacks. 2FA does not prevent injection.
Thus, Option B provides the most effective immediate protection.

The correct answer is D, Least privilege. In Linux, sudo temporarily grants elevated/root-level privileges to execute administrative commands. The CEH-aligned principle of least privilege requires that users, services, and processes receive only the minimum permissions needed to perform their authorized tasks. Allowing passwordless sudo for multiple commands weakens this control because a normal user can execute privileged actions without reauthentication, increasing the risk of accidental misuse, insider abuse, credential compromise, or privilege escalation. CEH materials emphasize least privilege as an authorization control and also note that sudo provides temporary root privileges. Zero trust is broader and focuses on continuous verification, defense in depth uses layered controls, and CIA refers to confidentiality, integrity, and availability. The specific misconfiguration here is excessive privilege assignment, so the violated security principle is least privilege. A secure configuration should tightly scope sudo permissions to only required commands and users, require authentication where appropriate, and log privileged actions.

SQL injection is one of the most common and dangerous vulnerabilities covered in CEH training. It occurs when an application accepts unsanitized input and directly passes it to a backend SQL query. To confirm the presence of SQL injection, the tester must insert a payload that alters the logic of the SQL query executed by the application. A classic test payload such as "1 OR 1=1 -" is widely used because it forces the database to return all rows instead of filtering based on the intended search value. This verifies whether the input field is being concatenated directly into a SQL command. The CEH methodology emphasizes starting with simple, non-destructive boolean-based payloads to safely evaluate the vulnerability without causing harm to the database or impacting server availability. Since directory traversal, brute-force login attempts, and XSS attacks target entirely different weaknesses, they are not appropriate for confirming SQL injection. The selected option aligns with proper CEH testing methodology for identifying insecure input handling and improper query construction.

This scenario precisely matches Time-Based Blind SQL Injection, a technique detailed in CEH v13 Web Application Hacking. When applications suppress error messages and sanitize outputs, attackers rely on response timing to infer whether injected SQL statements are executed.
In time-based SQL injection, the attacker injects database-specific delay functions (such as WAITFOR DELAY, DBMS_LOCK.SLEEP, or SLEEP()). If the injected condition is true, the database pauses execution, causing a noticeable delay.
The key indicators described-no visible output but increased response time-are classic signs of time- based SQL injection. CEH v13 explains that this method is particularly useful when:
* Errors are hidden
* UNION queries fail
* Output is not reflected
Union-based and out-of-band SQL injections require data exfiltration channels or visible outputs, which are absent here. "Heavy query-based" is not a formal CEH classification.
Thus, Option A is the correct answer.