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29. OWASP Top 10 Web Vulnerabilities

29.2 A03 Injection: SQL Injection

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Quick answer: the short, self-contained version of this lesson is the guide What Is SQL Injection and How to Prevent It.

SQL injection (SQLi) tevha hoto jevha user cha input thet SQL query madhe jato, ani attacker to query badalto. Chapter 21 madhe aapan sqlmap ne he baghitla; aata concept ani fix.

Vulnerable code (never do this):

// user input goes straight into the query
$id = $_GET['id'];
$sql = "SELECT * FROM users WHERE id = '$id'";

If the attacker sends id = 1' OR '1'='1, the query becomes ... WHERE id = '1' OR '1'='1' – which is always true and returns every row. Worse: 1'; DROP TABLE users;--.

The fix – prepared statements (parameterised queries):

// PDO: the input can never change the query structure
$stmt = $pdo->prepare("SELECT * FROM users WHERE id = ?");
$stmt->execute([$_GET['id']]);
$rows = $stmt->fetchAll();

The database treats the input strictly as data, never as SQL. This is exactly the approach you used in the Chapter 16 reels app. Also apply least-privilege DB users (Chapter 11) so a compromised app cannot drop tables.

Ravindra Bagale's Tip

"Remove quotes from the input (escaping)" is an old, incomplete fix. Prepared statements are the only correct fix – they keep the query and the data separate. We did exactly this in Chapter 16. Never join user input directly into a query.

Lab

In DVWA (SQL Injection, security = low), use 1' OR '1'='1 to dump all users. Then set security to "high" and try again – it fails. Open your reels app code and confirm every query uses prepared statements; fix any that do not.

Extended teaching notes

Why this lesson matters

Web flaws stay in the OWASP Top 10 because real apps still ship them. Your job is not to collect tool screenshots. It is to prevent and fix the class of bug on systems you own.

Apply the fix across stacks

Same class of bug, same idea in every language.

Java / Spring Boot

Parameterise queries, encode output, CSRF tokens, limited Actuator, dependency scanning.

ASP.NET Core

EF Core / parameterised SQL, Razor encoding, HTTPS, Data Protection.

Node.js / Express

helmet, parameterised SQL, npm audit, avoid eval and shell concat.

Python / Django / Flask / FastAPI

ORM, autoescape, pip-audit, Bandit; never shell=True with user input.

PHP / Laravel

PDO/Eloquent, Blade escaping, composer audit.

Go / Ruby

database/sql placeholders / ActiveRecord; html/template / ERB escaping; govulncheck / Brakeman.

nginx / Apache / Tomcat

Hide versions, TLS, security headers, least-open ports.

MySQL / PostgreSQL / MongoDB / Redis

Private networks, auth on, least-privilege users, no 0.0.0.0/0.

AWS / Azure / GCP

Roles not long-lived keys, private data stores, cloud audit logs on.

Real examples

Global: injection and XSS still appear in breach reports and bug bounties every year. Indian company (sample): a Bengaluru SaaS team maps each OWASP item to a CI check or a code-review question so new code cannot silently reintroduce it.

Mini case study

Suppose we are on a purple-team exercise for an Indian mid-size company (sample data). Red notes a technique from this lesson against a lab clone. Blue must show the control that stops it, the log that would have fired, and the ticket that hardens production. That is the standard this course trains you for.

Defender's worksheet (do this today)

  1. Write the lesson title, date and the exact lab target you are allowed to use.
  2. List three owned systems (VMs, apps, or cloud accounts) where this lesson applies.
  3. Run one safe check from the lesson on a lab system only. Paste the command and output.
  4. Write a two-sentence fix you would give a teammate.
  5. Name one related public advisory (CERT-In, CISA, NVD, or a vendor bulletin) with its date.

Indian workplace (sample data)

Suppose we are a junior analyst at Infosys, TCS, Wipro or a fintech SOC in Bengaluru/Pune. Turn this lesson into one checklist item with an owner, a due date and a place to store evidence (ticket + screenshot).

Global practice

Compare your notes with OWASP, CIS Benchmarks, NIST CSF/IR guidance or a cloud Well-Architected security question. Write five lines on what overlaps.

Everyday analogy

Explain the risk and the fix to a family member without jargon. If they can repeat the warning, you understand it well enough to teach juniors.

Key terms

  • Control: a safeguard (patch, config, process, detection).
  • Finding: a weakness backed by evidence.
  • Remediation: the fix plus how you verified it.
  • Scope: systems you have written permission to touch.
  • Least privilege: only the access the task needs.
  • Defence in depth: several layers so one failure does not end the story.

Common mistakes

  • Skipping written permission "just for a quick scan".
  • Practising on hostel, office or public targets without authorisation.
  • Collecting tool output without writing the fix.
  • Copying attack steps onto production to "verify". Defenders verify with versions, configs and patches.
  • Publishing screenshots that contain secrets, cookies or internal hostnames.

Recap

  • Evidence, fix, owner, date.
  • Own lab only.
  • Fix > spectacle.