Hacking Web Applications in Cyber Security: OWASP Threats and Defenses

Almost every product you build today is a web application — the banking portal, the food-delivery backend, the SaaS an Indian startup ships worldwide. Under the hood they are all HTTP requests, database queries, and rendered responses, and that ubiquity makes web applications the single largest attack surface in modern cyber security.

"Hacking web applications" sounds like an offensive skill, and for penetration testers it is. But the larger job market — and the more durable career — is defensive: the developers and application security engineers who understand these attacks well enough to make sure they never succeed. You cannot write a parameterized query without first understanding SQL injection.

Developer reviewing application security on multiple screens

This article walks through the major web application vulnerability categories — organized around the OWASP Top 10 themes — from a defender's chair, covering what each weakness is, its impact, and, above all, how developers shut it down. There are no exploit payloads here.

What the OWASP Top 10 Actually Is

The OWASP Top 10, from the Open Worldwide Application Security Project, is a community-maintained, ranked snapshot of the vulnerability classes that appear most often in real applications. It is not a compliance standard — treat it as the syllabus every web developer should master first. Most are ordinary design and coding weaknesses, closed by developers who know the right pattern.

Injection (Including SQL Injection)

What it is. Injection happens when untrusted user input is mixed directly into a command or query that an interpreter then executes — SQL, but also OS commands, LDAP, or NoSQL. The interpreter cannot tell the developer's code from the attacker's fragment, so it runs both.

Impact. A successful SQL injection can read entire user tables, bypass a login, alter records, and sometimes fully compromise the server. For a fintech or e-commerce firm, one injectable endpoint can expose every customer's data.

How developers defend against it. The root cause is mixing data with code, so keep them separate:

Use parameterized queries (prepared statements) everywhere — the query structure is fixed first, and input is passed as data that can never become SQL. Safe ORMs and query builders do this by default.
Validate and constrain input (type, length, allowlist) as defense in depth — never as the only control.
Give the database account least privilege so a compromised query cannot drop tables.

Parameterization in practice

# Vulnerable: user input concatenated into the query string
query = "SELECT * FROM users WHERE email = '" + user_input + "'"

# Safe: parameterized — the driver treats user_input strictly as data
cursor.execute("SELECT * FROM users WHERE email = %s", (user_input,))

Never build a query by string concatenation.

Cross-Site Scripting (XSS)

What it is. XSS occurs when an application includes untrusted input in a page sent to other users without neutralizing it. The victim's browser then runs attacker-controlled script as if it came from your trusted site.

Impact. Stolen session cookies, hijacked accounts, keylogged input, and phishing overlays served from a legitimate domain — a direct path to account takeover.