-1" OR 5*5=25 --

It looks like a classic SQL injection payload.

What it does (in a SQL context):

• The part 5*5=25 is a boolean expression that evaluates to true.
• The OR means the overall condition becomes true regardless of the other side.
• The trailing -- starts a SQL comment, so the rest of the query is ignored.
• The -1" is typically used to terminate a string literal started by the attacker.

In short: it’s an attempt to bypass checks by injecting a tautology and commenting out the rest of the query.

Defensive takeaway (exam-ready):

• Use parameterized queries/prepared statements (never concatenate user input into SQL).
• Validate and sanitize inputs; apply least privilege to the DB user.
• Use ORM/query builders that separate code and data.
• Avoid dynamic SQL where possible; if needed, use proper escaping and allowlists.
• Consider WAFs and input-length checks to reduce risk.

If you want, I can show a safe example in a language you’re studying (e.g., Python with psycopg2, Java with PreparedStatement) or explain how to detect and mitigate such patterns in exam questions. Do you want a concrete code example?