-1" OR 5*5=26 --

That looks like an SQL injection payload.

• What it’s doing (in general):

  • -1" tries to terminate an existing string literal in a vulnerable SQL statement.
  • OR 55=26 adds another condition to the WHERE clause. Since 55 = 25, 25 ≠ 26, so that particular expression evaluates to false.
  • -- comments out the rest of the SQL statement, so the rest of the query is ignored.

• Why this matters: In a poorly parameterized query (built by string concatenation), an attacker can alter the logic of the query, potentially bypass authentication or reveal data.

• Safety note: Do not test or exploit systems you don’t own or have explicit permission to test. It’s illegal and harmful.

• How to defend against it (exam-ready summary):

  • Use prepared statements / parameterized queries (bind user input as data, not as part of SQL).
  • Avoid building SQL by string concatenation; use ORM or safe DB libraries.
  • Implement input validation and type checking; limit lengths.
  • Principle of least privileges for the database user.
  • Enable proper error handling and avoid leaking DB errors.
  • Consider WAFs and regular security testing in a controlled environment.

If you’re studying for an exam, I can tailor a concise definition, an example of vulnerable vs. secure code, or a short Q&A on SQL injection basics.