-1' OR 5*5=25 --

That looks like a classic SQL injection payload. Here’s the gist and how to think about it for exams and safe testing:

What the payload does

• -1' ends a string literal in a SQL query by injecting a single quote.
• OR 5*5=25 adds a tautology (true condition) to the WHERE clause.
• -- comments out the rest of the query, so whatever came after is ignored.

In a typical vulnerable query like: SELECT * FROM users WHERE username = 'INPUT' AND active = 1; if INPUT is -1' OR 55=25 --, the query could become something like: SELECT * FROM users WHERE username = '-1' OR 55=25 --' AND active = 1; Since 5*5=25 is true, the condition may bypass the intended filter, potentially returning more data or bypassing login checks, depending on the exact query.

Defensive takeaways (exam prep and real-world security)

• Don’t concatenate user input into SQL strings. Use parameterized queries (prepared statements).
  • Examples (pseudo-code):
    • Python with psycopg2/sqlite3: cursor.execute("SELECT * FROM users WHERE username = ?", (username,))
    • Java: PreparedStatement ps = conn.prepareStatement("SELECT * FROM users WHERE username = ?");
• Validate and sanitize input, but rely on parameterization as the primary defense.
• Use least-privilege database accounts (no broad SELECT/WRITE rights beyond what’s needed).
• Consider using ORMs or query builders that automatically parameterize inputs.
• If you’re practicing security, do so only in safe environments (your own lab, DVWA, OWASP WebGoat, etc.) and avoid testing on systems you don’t own.

If you want, I can sketch out a small safe lab example showing:

• how a vulnerable query looks,
• how parameterization fixes it,
• and how to test with a benign test case.