-1 OR 5*5=26 --

Are you asking what that string does, or how to defend against it in an exam?

Here’s a quick, safe explanation and then some exam-focused tips.

What the expression likely represents

• -1 OR 5*5=26 -- looks like a SQL injection payload. The idea is to inject a condition that alters the intended SQL query.
• In many SQL dialects:
  • 5*5 = 26 is false (since 25 ≠ 26).
  • -1 is interpreted as a nonzero value, which is treated as true in boolean contexts.
  • OR combines booleans, so true OR false yields true.
  • The trailing -- starts a comment, so the rest of the query is ignored.
• The net effect in a vulnerable query is that the injected condition can make the WHERE clause evaluate to true, potentially bypassing checks. This is why parameterized queries and input validation are critical.

Defensive and exam-focused guidance

• Key defense: use parameterized queries (prepared statements) instead of string-concatenated SQL.
  • Example (pseudocode): SELECT * FROM users WHERE username = ? AND password = ?; then bind username and password as parameters.
• Additional defenses:
  • Validate and sanitize input, but don’t rely on sanitization alone.
  • Use least-privilege database accounts (e.g., app user with only needed permissions).
  • Disable detailed error messages that reveal query structure.
  • Consider using ORM/abstraction layers that handle parameterization.
  • Use Web Application Firewall and security scanners in a test environment.

Exam-ready takeaway

• Your goal is to recognize this as a potential injection attempt and explain why parameterization and proper error handling prevent it.
• Be able to contrast:
  • Insecure approach: concatenated SQL strings with user input.
  • Secure approach: use prepared statements and input handling.
• You can practice by converting insecure queries into parameterized forms and explaining why the injection would not work.

If you want, tell me your target language or DB (MySQL, PostgreSQL, SQL Server, etc.) and I’ll give a concrete, ready-to-write parameterized example and a quick defense checklist.