-1' OR 5*5=25 or 'xSFajc1b'='

It looks like an SQL injection payload. The string is designed to tamper with a query by closing a string literal and injecting an always-true condition.

What’s happening conceptually

• The sequence -1' tries to close a previous string literal in the SQL statement.
• OR 55=25 inserts a boolean condition. Since 55=25 is mathematically true, this makes the WHERE clause effectively always true (a tautology) if the input is concatenated into SQL without proper binding.
• The rest (or 'xSFajc1b'='...) is another tautological or benign-looking fragment that is intended to keep the logic from failing and exploit the query’s structure.

Why it’s a risk

• If user input is concatenated into SQL, an attacker can bypass filters, authentication, or retrieve more data than intended by turning the WHERE clause into something always true.
• It only needs to work in specific vulnerable code paths (e.g., where user input is directly inserted into the SQL string).

Defenses you should know for exams

• Use parameterized queries (prepared statements) everywhere. Bind user input as data, not as part of the SQL string.
  • Example idea (pseudocode):
    • SELECT ... FROM users WHERE username = ? AND password = ?
    • Bind username and password as parameters, not by string concatenation.
• Avoid dynamic SQL that concatenates user input.
• Use stored procedures with parameter binding, not building SQL strings from user input.
• Implement input validation and allowlists where possible, but don’t rely on validation alone to prevent injections.
• Apply the principle of least privilege: run the application with a DB user that has only the necessary rights.
• Use ORM layers or query builders that automatically parameterize inputs.
• Enable and monitor security controls: WAF rules for injection patterns, logging of suspicious inputs, and regular security reviews.

Quick recap

• The string is a classic SQL injection attempt using a tautology (5*5=25) to alter the query logic.
• The remedy is to always parameterize queries and follow secure coding practices to prevent such injections.

If you’d like, I can show a concrete before/after example in a specific language (Python, Java, PHP) to illustrate how parameter binding fixes this.