Decoded, that string is:
X4bwFTJY'; waitfor delay '0:0:15' --
What it is (high level)
- It looks like a time‑based SQL injection attempt. The attacker closes a quoted value, injects a wait/delay command (waitfor delay '0:0:15' causes a 15‑second pause on MS SQL Server), then comments out the remainder of the query with --.
- An attacker uses this pattern to test whether untrusted input is being passed raw into SQL: if the application’s response is delayed by about 15 seconds, that suggests the injection was executed.
What to do if you see this
- Treat it as a potential attack and investigate: check web server and database logs, correlate IPs and timestamps, and look for other suspicious inputs or abnormal queries.
- Check whether any sensitive data was accessed or exfiltrated. If you suspect compromise, follow your incident response process (isolate, contain, preserve evidence, rotate credentials if needed).
How to prevent (defensive measures)
- Use parameterized queries / prepared statements (never concatenate untrusted input into SQL).
- Apply strict input validation and output encoding on all inputs.
- Give database accounts the least privileges needed; avoid running apps with admin/db owner privileges.
- Enforce query timeouts and resource limits in the database and application.
- Use an ORM or stored procedures that accept parameters (but still ensure parameters are used correctly).
- Deploy WAFs and intrusion detection/logging to block or alert on common injection patterns.
- Keep DBMS and application frameworks patched.
- Regularly perform authorized security testing (and only with permission).
If you’re testing an application
- Only perform tests against systems you own or have explicit permission to test. Unauthorized testing is illegal and unethical.
- Use authorized tooling and follow a safe testing methodology.
If you want, tell me where you saw this (e.g., logs, form input) and whether you have access to the application’s code or DB configuration — I can suggest specific investigation and mitigation steps for your environment.