Question

555-1 OR 942=(SELECT 942 FROM PG_SLEEP(15))--

Answer 1

That string is a time-based SQL‑injection payload targeting PostgreSQL. Briefly:

What it does
- 555-1 evaluates to 554. The OR clause then executes: 942 = (SELECT 942 FROM pg_sleep(15)).
- Using pg_sleep(15) causes the database to pause for 15 seconds; if the subquery returns 942 after the sleep, the comparison becomes true, making the whole expression true and causing an observable delay.
- An attacker can use this to detect blind SQL injection (if the application response is delayed, it’s likely vulnerable).

Important: only run tests like this against systems you own or have explicit permission to test.

How to fix / mitigate
- Use parameterized/prepared statements (never build SQL by concatenating user input). Example:
- Python (psycopg2): cursor.execute("SELECT * FROM items WHERE id = %s", (user_id,))
- Node (pg): client.query("SELECT * FROM items WHERE id = $1", [userId])
- Validate and whitelist input (e.g., if expecting an integer, enforce integer parsing and bounds).
- Principle of least privilege: use a DB account with minimal permissions for the application; avoid using superuser or overly-permissive accounts.
- Avoid exposing dangerous functions where feasible; audit DB functions and revoke unnecessary rights.
- Use a Web Application Firewall (WAF), request throttling, and good logging/monitoring to spot unusual delays or injection attempts.
- Perform authorized security testing in a controlled environment (staging) and/or hire a professional penetration tester or use automated scanners with permission.

If you want, paste the vulnerable query or code (from the app) and I can show how to convert it safely to a parameterized form or suggest specific fixes.