Most Common Security Vulnerabilities in Web Apps (2025 Update)

Web applications are a prime target for cyberattacks, and failing to secure them can lead to data breaches, financial loss, and reputational damage. Here are the most common web security vulnerabilities and how to prevent them.

1️⃣ SQL Injection (SQLi) 🛑

❌ What It Is:

Attackers manipulate SQL queries to access, modify, or delete a database.

⚡ Example Attack:

sql
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SELECT * FROM users WHERE username = 'admin' OR '1'='1'; 

If not secured, this can bypass authentication and expose sensitive data.

✅ Prevention:

✔️ Use Parameterized Queries and Prepared Statements:

python
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cursor.execute("SELECT * FROM users WHERE username = ?", (user_input,)) 

✔️ Use ORMs (SQLAlchemy, Hibernate) to handle database queries safely.

2️⃣ Cross-Site Scripting (XSS) 💻

❌ What It Is:

Attackers inject malicious JavaScript into web pages, tricking users into executing scripts in their browsers.

⚡ Example Attack:

html
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<script>alert('Hacked!')</script> 

If an app doesn’t sanitize user input, this script could steal cookies or inject malware.

✅ Prevention:

✔️ Escape and sanitize all user input before rendering.
✔️ Use Content Security Policy (CSP) to restrict JavaScript execution.
✔️ Use libraries like DOMPurify to filter malicious scripts.

3️⃣ Cross-Site Request Forgery (CSRF) 🎭

❌ What It Is:

An attacker tricks a logged-in user into unknowingly executing actions on their behalf.

⚡ Example Attack:

A hacker sends a user a malicious link like:

html
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<img src="https://bank.com/transfer?amount=1000&to=attacker" /> 

If the user is logged in, the request executes without their consent.

✅ Prevention:

✔️ Use CSRF tokens for every sensitive request.
✔️ Enforce SameSite cookie attributes to prevent unauthorized requests.
✔️ Require re-authentication for critical actions.

4️⃣ Broken Authentication 🔑

❌ What It Is:

Weak login mechanisms allow brute force attacks, credential stuffing, or session hijacking.

⚡ Example Attack:

Using weak passwords like admin123, or session fixation, where an attacker hijacks a valid session.

✅ Prevention:

✔️ Enforce strong passwords & Multi-Factor Authentication (MFA).
✔️ Implement rate-limiting & account lockout for failed login attempts.
✔️ Use secure session management (e.g., session expiration, HttpOnly cookies).

5️⃣ Security Misconfigurations ⚠️

❌ What It Is:

Leaving debug mode enabled, exposing sensitive error messages, or using default credentials.

⚡ Example Attack:

• Exposed .git repositories revealing sensitive code.
• Default admin credentials (admin/admin) still enabled.

✅ Prevention:

✔️ Disable debugging in production (DEBUG=False in Django).
✔️ Regularly review server & database configurations.
✔️ Enforce least privilege access for all services.

6️⃣ Insecure Direct Object References (IDOR) 🔓

❌ What It Is:

Users access unauthorized resources by modifying request parameters.

⚡ Example Attack:

A user changes a URL from:

url
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https://bank.com/user/profile?id=123 

to

url
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https://bank.com/user/profile?id=124 

This allows them to view another user's account if authorization isn’t enforced.

✅ Prevention:

✔️ Use proper access control (check user permissions on every request).
✔️ Avoid exposing predictable IDs—use UUIDs instead.
✔️ Implement server-side authorization checks for every request.

7️⃣ Server-Side Request Forgery (SSRF) 🌐

❌ What It Is:

Attackers manipulate a server to make internal network requests (e.g., accessing admin panels, metadata services).

⚡ Example Attack:

A web app allows users to fetch URLs, but an attacker requests:

url
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https://internal-server/admin 

This exposes internal infrastructure.

✅ Prevention:

✔️ Whitelist allowed external domains (block internal IP access).
✔️ Use a network firewall to prevent unauthorized access.
✔️ Validate user input to prevent arbitrary URL fetching.

8️⃣ Insufficient Logging & Monitoring 🕵️

❌ What It Is:

Without proper logs, attacks go unnoticed, allowing data breaches to persist.

⚡ Example Attack:

• Unauthorized access but no alerts are triggered.
• Failed login attempts aren’t logged, enabling brute force attacks.

✅ Prevention:

✔️ Enable real-time monitoring with SIEM tools (Splunk, ELK).
✔️ Set up alerts for suspicious activities (e.g., multiple failed logins).
✔️ Store logs securely to prevent tampering.

9️⃣ Unvalidated Redirects & Forwards 🔀

❌ What It Is:

Attackers manipulate URLs to phish users by redirecting them to malicious sites.

⚡ Example Attack:

url
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https://yourbank.com/login?redirect=http://evil.com 

A user clicks, thinking it's safe, but lands on a fake login page.

✅ Prevention:

✔️ Use a fixed set of redirect URLs (avoid dynamic redirects).
✔️ Validate all redirect parameters before processing them.
✔️ Use rel="noopener noreferrer" for external links.

🔐 Final Takeaways: Stay One Step Ahead of Hackers!

✔️ Sanitize & validate all user input to prevent SQLi & XSS.
✔️ Enforce strong authentication & session management to prevent account hijacking.
✔️ Regularly update dependencies & monitor logs for vulnerabilities.
✔️ Implement security headers (CSP, X-Frame-Options) to harden web apps.

🚀 Pro Tip: Use OWASP ZAP & Burp Suite to scan your web apps for vulnerabilities!