-1" OR 5*5=26 --

That looks like a classic SQL injection payload. Here’s what it’s trying to do, in simple terms:

• -1" attempts to close a preceding string literal in an SQL statement.
• OR 55=26 adds a condition to the WHERE clause. Since 55=25, the comparison 25=26 is false.
• -- starts a comment, so the rest of the original query is ignored.

How it plays out depends on the exact query context:

• If the query is something like: SELECT * FROM users WHERE username = "-1" OR 5*5=26 -- Then the condition after OR is false (25=26), and the part after -- is ignored. The query effectively becomes: username = "-1" (i.e., you’re just checking for -1 as a username).
• This does not reliably bypass authentication. An attacker would typically use something like OR 1=1 -- to always make the WHERE clause true, which is the classic bypass.

Why this matters for exams and real life:

• It illustrates three core ideas of SQL injection:
  • Breaking out of a quoted string
  • Injecting a logical OR condition
  • Commenting out the rest of the query
• It also shows why parameterized queries and input validation are essential.

Defensive measures you should know for exams:

• Use prepared/parameterized statements (no string concatenation of user input into SQL).
• Validate and constrain inputs (type checks, length checks, allowlists).
• Use least-privilege database accounts (no excess permissions).
• Avoid detailed error messages that reveal SQL syntax.
• Consider using ORM layers or stored procedures with careful handling of inputs.

If you want, I can show a safe, parameterized example in your language of choice (e.g., Python with psycopg2, Java with JDBC, etc.), or walk through more exam-style questions about SQL injection.