[질문] -1' OR 2+834-834-1=0+0+0+1 or 'NYIXsTe5'='

That string looks like an SQL‑injection payload (or an attempt at one). It’s built to break out of an intended value and inject a boolean expression that evaluates to true so the surrounding SQL condition will be satisfied.

Quick breakdown

• The fragment -1' likely closes an existing quoted value in the application’s SQL.
• 2+834-834-1 = 0+0+0+1 evaluates to 1 = 1, which is true.
• The OR ... part makes the whole WHERE (or authentication) condition evaluate true even if the intended check would have failed.
• The trailing or 'NYIXsTe5'=' is another tautology-style expression (although as written it’s a comparison of a non‑empty string to an empty side, which is false; the earlier true clause is sufficient).

Why this is dangerous

• If an application concatenates user input directly into SQL, an attacker can change query logic (bypass authentication, exfiltrate data, delete rows, etc.).
• SQL injection is one of the most common and severe web vulnerabilities.

How to prevent it (recommended, prioritized)

1. Parameterized queries / prepared statements (use placeholders; never concatenate user input into SQL). This is the single most effective mitigation.
2. Use an ORM or high‑level DB library that uses parameterization by default.
3. Validate and constrain input (type checks, length limits, allow‑lists).
4. Principle of least privilege for DB accounts (don’t use a DBA account from the app).
5. Use stored procedures carefully (still require parameterization).
6. Escape user input only as a last resort and with correct, DB‑specific escaping.
7. Logging, monitoring, WAFs, and regular security testing (in controlled environments) and code review. Safe examples (parameterized queries)

• Python (sqlite3 / DB‑API) cursor.execute("SELECT * FROM users WHERE username = ? AND password = ?", (username, password))

• PHP (PDO) $stmt = $pdo->prepare("SELECT * FROM users WHERE username = :u AND password = :p"); $stmt->execute([':u' => $username, ':p' => $password]);

• C# (SqlClient) using var cmd = new SqlCommand("SELECT * FROM users WHERE username = @u AND password = @p", conn); cmd.Parameters.AddWithValue("@u", username); cmd.Parameters.AddWithValue("@p", password);

If you’re trying to harden an app, I can:

• Review code snippets and point out injection risks,
• Show how to convert a vulnerable query to a parameterized one for your specific language/DB,
• Or recommend testing steps (tools and safe practices) for a controlled security assessment.

If you intended something else with that string, tell me the context (where it came from and what you want to do) and I’ll tailor the advice.