-1" OR 5*5=25 --

That looks like a classic SQL injection payload.

What it is doing (at a high level):

• It tries to terminate a string literal in a SQL query and injects a tautology (something that’s always true).
• 55=25 is true, so OR 55=25 makes the WHERE clause true for all rows.
• The trailing -- is a comment, so the rest of the original query is ignored.

Example (simplified, vulnerable code):

• Vulnerable query: SELECT * FROM users WHERE username = 'USER_INPUT' AND password = 'PWD';
• If USER_INPUT = -1' OR 55=25 --, the query becomes: SELECT * FROM users WHERE username = '-1' OR 55=25 --' AND password = 'PWD'; The part after -- is ignored, and the WHERE clause reduces to a tautology, potentially bypassing authentication.

Notes on quoting:

• In many setups, input is placed inside single quotes. A payload like -1' OR 5*5=25 -- can work similarly.
• Some databases use double quotes or different quote rules; the idea is to break out of the string and inject a condition that’s always true.

Defenses (exam-relevant):

• Use parameterized queries / prepared statements (do not concatenate user input into SQL).
• Validate and sanitize inputs; apply least-privilege database accounts.
• Use stored procedures, ORMs with bound parameters.
• Enable proper error handling and avoid leaking DB error messages.
• Consider input whitelisting for fields that expect specific formats.

Possible exam prompt practice:

• Explain why -1' OR 1=1 -- would also be a common payload.
• Describe how parameterized queries prevent this kind of attack.
• Compare the security impact of this payload if:
  • The application uses single quotes around user input.
  • The application uses no escaping and directly concatenates input into the SQL.

If you want, I can tailor explanations to a specific database (MySQL, PostgreSQL, SQL Server) or give a short practice question.