-1' OR 5*5=26 --

It looks like a classic SQL injection payload.

What it does in a vulnerable query (conceptually):

• The input tries to break out of a string literal and add an OR condition: -1' OR 5*5=26 --.
• If a query is built by concatenating user input, the injected part can alter the WHERE clause.
• The -- starts a comment in SQL, so the rest of the query is ignored. The effect depends on the exact query, but the goal is typically to bypass authentication or modify the logic.

Why 55=26 matters here: 55 evaluates to 25, so 5*5=26 is false in most databases. The payload’s effectiveness depends on the surrounding query. More common bypass payloads use conditions like 1=1 or ' OR '1'='1 to always be true.

Defensive notes (exam-prep and real-world):

• Never build SQL by concatenating user input. Use parameterized queries or prepared statements.
• Validate and sanitize input, and enforce proper data types (e.g., numeric fields as numbers, not strings).
• Use least-privilege database accounts (no broad SELECT/UPDATE permissions if not needed).
• Disable or sanitize detailed error messages that reveal SQL structure.
• Consider using ORMs or query builders that automatically parameterize inputs.

If you want, I can show:

• A safe version of a login query (parameterized example in your language of choice).
• A quick checklist of common injection patterns and how to guard against them.