5550'XOR(555*if(now()=sysdate(),sleep(15),0))XOR'Z

That string looks like a time-based blind SQL injection payload intended for MySQL. I can’t help you exploit live systems, but I can explain what it illustrates and how to defend against it for exam prep.

What this payload is illustrating (high level)

• Time-based blind SQL injection: The attacker doesn’t read data directly from the database. Instead, they cause a delay (sleep) and infer whether a condition is true based on response time.
• The core idea: if a guessed condition evaluates to true, the database runs sleep(15) (pause for 15 seconds); otherwise it does something harmless like 0.
• now() vs sysdate(): These are MySQL date/time functions. NOW() returns a timestamp that is constant for the duration of a statement, while SYSDATE() can return a newer timestamp on subsequent evaluations within the same statement. In practice, this can be used to craft a condition that is only true under certain timing circumstances, aiding the attacker in inference.
• The surrounding syntax (the 5550’XOR(555*... )XOR’Z part) is an obfuscated way to break out of a quoted string in an SQL statement, insert a conditional expression, and then continue the rest of the query. XOR here is used as part of the payload’s obfuscation to avoid simple string-based filtering.

Key defensive takeaways (exam-friendly)

• Use parameterized queries prepared statements everywhere. Do not concatenate user input into SQL strings.
• Prefer an ORM or properly bound variables to ensure inputs are treated as data, not executable code.
• Validate and sanitize inputs, and implement allowlists for expected data formats (e.g., numeric IDs only).
• Apply the principle of least privilege: run the app’s database user with only the permissions it strictly needs; use read-only accounts where appropriate.
• Consider enabling general application-level protections:
  • Web Application Firewall (WAF) rules to flag suspicious patterns (e.g., sleep(...) usage, time-based delays, unusual function calls).
  • Implement strict query timeout handling in the application to prevent long delays.
• Security testing should be done in a safe, controlled environment (lab with intentionally vulnerable apps such as DVWA/bWAPP) and with explicit authorization.

Possible exam question you could practice

• Explain how a time-based blind SQL injection works. What roles do NOW() and SYSDATE() typically play in such payloads? Why is SLEEP() used, and what would a defender look for in logs to detect this? What are the best mitigations to prevent this class of vulnerability?

If you want, I can tailor a short practice quiz or create a few example exam-style questions with model answers on SQL injection and related defenses.