OWASP Top 10 2025 Complete Guide

The OWASP Top 10 is a list of the 10 most dangerous security weaknesses found in web applications. Think of it like a "Most Wanted" list of bad guys that attackers are constantly trying to exploit.

OWASP stands for Open Web Application Security Project, a nonprofit organization that helps make software more secure. Every few years, they release an updated list showing which vulnerabilities are most common and dangerous.

Why does this matter? Because if you're a developer, tester, business owner, or just someone who uses web applications, understanding these vulnerabilities helps you protect yourself and your organization.

Nearly 50 percent of all web applications contain at least one vulnerability from this list. That's not a theoretical problem. That's real risk affecting real people every day.

The 2025 edition was just released in November 2025, based on analyzing over 175,000 CVEs (Common Vulnerabilities and Exposures) and feedback from security professionals worldwide.

The 10 OWASP Top 10 Vulnerabilities for 2025

1. Broken Access Control (A01:2025)

What It Means in Simple Terms:

Imagine a bank where anyone could walk into the vault, take out money, and walk away. No one checks whether you're allowed to be there. That's broken access control. It's when a system fails to properly verify what you're allowed to do.

Real-World Example:

You're logged into your banking app and you can view your account balance at this URL: yourbank.com/account?user_id=1234

An attacker notices the user_id in the URL and tries changing it: yourbank.com/account?user_id=5678

If the bank doesn't properly check whether you're allowed to see user 5678's account, the attacker sees someone else's financial information. This is called an insecure direct object reference (IDOR).

How Attackers Exploit It:

Changing URLs or parameters to access other people's data

Accessing admin features without being an admin

Performing actions (like deleting accounts) you shouldn't be able to perform

Manipulating tokens or session cookies to impersonate others

How to Prevent It:

Always verify that users can only access what they're supposed to access

Use proper authentication and authorization checks on every single action

Create different user roles (admin, user, guest) with appropriate permissions

Log all access attempts so you can detect suspicious behavior

Test your access controls thoroughly

2. Security Misconfiguration (A02:2025)

What It Means in Simple Terms:

Security misconfiguration is when you set up your application incorrectly, leaving doors wide open for attackers. It's like having a security system but forgetting to turn it on.

This became the #2 vulnerability in 2025, jumping from #5 in the previous list.

Real-World Example:

You deploy a web application but forget to:

Remove default admin credentials (username: admin, password: admin)

Turn off debug mode (which shows detailed error messages revealing sensitive information)

Disable directory listing (so attackers can see all files on the server)

Configure proper file permissions (so sensitive files are readable by anyone)

Remove example/test files from production

Any of these mistakes gives attackers an easy way in.

How Attackers Exploit It:

Using default credentials to log in as admin

Reading verbose error messages that leak information about your system

Accessing sample files left behind during development

Modifying configuration files

Reading sensitive information from exposed .env files or config files

How to Prevent It:

Use automated tools that check for misconfiguration

Never leave default usernames and passwords

Turn off debug mode in production

Use a minimal configuration with only what you need enabled

Regularly audit your systems to find misconfigurations

Use configuration management tools to ensure consistent, secure setups

3. Software Supply Chain Failures (A03:2025)

What It Means in Simple Terms:

Your application doesn't exist in isolation. It uses libraries, frameworks, and tools from other companies. If any of those libraries are compromised (infected with malicious code), your entire application becomes compromised.

Think of it like the water supply. Your home has clean water because the water utility companies ensure purity at their facilities and in the pipes. If someone poisons the water at the source, everyone using that water gets poisoned.

Real-World Example:

You build an application using thousands of open-source libraries (this is normal). One of these libraries gets compromised by attackers who inject malicious code. You update your library to the latest version without realizing it's been poisoned. Your application now contains malicious code.

This actually happened in 2020 with SolarWinds, where 18,000 organizations unknowingly installed malicious updates.

How Attackers Exploit It:

Compromising popular open-source libraries and injecting malicious code

Attacking the development environment where libraries are built

Intercepting downloads to insert malicious code

Creating fake versions of popular libraries with slightly misspelled names

Compromising the build servers that create software updates

How to Prevent It:

Keep a detailed list of all libraries and dependencies your application uses (called SBOM - Software Bill of Materials)

Regularly scan dependencies for known vulnerabilities

Use tools that verify the integrity of downloads

Only download from official sources

Pin your dependency versions so you're not automatically downloading updates without review

Monitor security advisories for libraries you use

Use private/internal repositories if possible to maintain control

4. Cryptographic Failures (A04:2025)

What It Means in Simple Terms:

Cryptography is the math that protects sensitive information like passwords, credit card numbers, and personal data. Cryptographic failures happen when this protection is broken, outdated, or improperly implemented.

Real-World Example:

A website stores passwords using an old encryption method from the 1990s. Today's computers are so fast they can break this encryption in minutes. An attacker hacks the database and quickly decrypts all the passwords.

Another example: A website sends your credit card number over regular HTTP (unencrypted) instead of HTTPS. Attackers on the same WiFi network intercept it and steal your card number.

How Attackers Exploit It:

Breaking weak encryption

Intercepting unencrypted data sent over the internet

Using decrypted data from stolen databases

Finding hardcoded encryption keys in source code

Using outdated encryption algorithms

How to Prevent It:

Always use HTTPS for any data transmission

Never store passwords in plain text or using weak encryption

Use modern encryption algorithms (AES-256 for symmetric, RSA-2048+ for asymmetric)

Use strong, randomly generated encryption keys

Encrypt sensitive data at rest (when stored) and in transit (when traveling)

Never hardcode encryption keys in your code

Use proper key management systems

5. Injection (A05:2025)

What It Means in Simple Terms:

Injection happens when an attacker puts malicious code into your application through user input. The application then executes this malicious code thinking it's legitimate.

Think of it like telling a restaurant to "make me pasta" but actually saying "make me pasta, then send all customer credit card numbers to the attacker's server". If the restaurant just follows the instructions literally, it will do both.

Real-World Example:

You have a login form with username and password fields. An attacker enters: admin' -- as the username.

If the application builds a database query like this:

SELECT * FROM users WHERE username = 'admin' --' AND password = '...'

The -- character in SQL means "ignore everything after this". So the query becomes:

SELECT * FROM users WHERE username = 'admin'

The attacker logs in as admin without knowing the password.

How Attackers Exploit It:

SQL Injection (manipulating database queries)

NoSQL Injection (manipulating database queries in NoSQL databases)

Cross-site Scripting (XSS) - injecting malicious JavaScript

Command Injection (executing system commands)

LDAP Injection (manipulating directory services)

How to Prevent It:

Never directly include user input in queries or commands

Use prepared statements or parameterized queries

Validate and sanitize all user input

Use allowlists to only accept expected input

Never trust user input, ever

Use web application firewalls to detect injection attempts

6. Insecure Design (A06:2025)

What It Means in Simple Terms:

Insecure design means the fundamental architecture and business logic are flawed from the beginning. It's not a coding mistake. It's a design mistake.

Real-World Example:

An online store has a password reset feature that doesn't verify your identity well. An attacker could reset anyone's password by just knowing their username. This isn't a bug in the code, it's a flawed design.

Another example: An e-commerce site lets you manipulate the price before checkout. An attacker changes the price of a $500 item to $0.01 and completes the purchase. The design didn't include proper validation.

How Attackers Exploit It:

Exploiting weak password reset mechanisms

Manipulating business logic (like changing prices)

Bypassing authorization checks designed poorly

Finding loopholes in workflows

How to Prevent It:

Use threat modeling to think about how attackers might abuse your system

Document and review security requirements

Have security reviews before implementation, not after

Test edge cases and unusual scenarios

Validate all data and transactions on the server side

Implement proper authorization checks in business logic

7. Authentication Failures (A07:2025)

What It Means in Simple Terms:

Authentication is how you prove you're really you. Failures happen when this protection is weak. It's like a bouncer at a club who accepts a fake ID.

Real-World Example:

A website lets you change your password without entering your current password. An attacker can just change someone else's password without permission.

Another example: A website doesn't use two-factor authentication (2FA) for important actions. An attacker gets your password and gains full access.

How Attackers Exploit It:

Using weak or common passwords

Brute-forcing password attempts without limits

Reusing usernames/passwords across sites

Session hijacking (stealing session tokens)

Lack of two-factor authentication

How to Prevent It:

Require strong passwords (minimum length, complexity)

Implement rate limiting (limit login attempts)

Use two-factor authentication for important actions

Properly manage sessions (timeout, invalidation)

Don't store passwords in plain text (use hashing)

Use proper authentication libraries instead of building your own

8. Data Integrity and Verification Failures (A08:2025)

What It Means in Simple Terms:

Data integrity means your data is trustworthy and hasn't been tampered with. Failures occur when you don't verify that data is legitimate.

Real-World Example:

A software library is updated without any verification. An attacker intercepts the download and replaces it with malicious code. You install the "update" and your system is now compromised.

Another example: An application deserializes (converts) data from users without checking if it's safe. An attacker sends specially crafted data that executes malicious code.

How Attackers Exploit It:

Tampering with software updates

Manipulating serialized data

Modifying configuration files

Creating fake plugins or extensions

How to Prevent It:

Verify digital signatures on all updates

Check integrity with checksums or hashes

Safely deserialize data (or avoid it altogether)

Use secure serialization formats

Control which plugins and extensions can be used

Sign all important data

9. Security Logging and Monitoring Failures (A09:2025)

What It Means in Simple Terms:

Logging is recording what happens in your application. Monitoring is watching those logs to detect suspicious activity. Failures happen when you don't log important events or don't monitor the logs.

Real-World Example:

An attacker breaks into your system and deletes the logs that would show what they did. Nobody knows an attack happened.

Another example: Your application logs everything, but nobody ever looks at the logs. An attacker could be stealing data for months and nobody notices.

How Attackers Exploit It:

Performing attacks without leaving evidence (because logging is disabled)

Deleting logs after breaking in

Knowing that no one monitors for suspicious activity

How to Prevent It:

Log all important events (logins, failed logins, data access, privilege changes)

Send logs to a secure location where they can't be deleted

Monitor logs in real-time for suspicious patterns

Alert security teams when suspicious activity is detected

Keep logs for adequate periods (typically 1-2 years minimum)

Protect logs with strong access controls

10. Mishandling of Exceptional Conditions (A10:2025) - NEW!

What It Means in Simple Terms:

This is a brand new category for 2025. It covers what happens when your application encounters errors or unexpected situations. If error handling is bad, attackers can exploit these edge cases.

Real-World Example:

Your application crashes when it runs out of disk space. An attacker fills up the disk and crashes your service (denial of service).

Another example: Your application displays detailed error messages showing database passwords or system information. An attacker uses this information to plan further attacks.

How Attackers Exploit It:

Sending unexpected input that causes errors

Reading sensitive information from error messages

Triggering out-of-memory errors

Causing resource exhaustion

Using error conditions to bypass security checks

How to Prevent It:

Handle all exceptions gracefully (don't crash)

Never show detailed error messages to users

Log detailed errors internally for debugging

Define what "secure failure" means (usually deny access)

Test with extreme inputs and edge cases

Implement resource limits to prevent exhaustion

Key Changes from 2021 to 2025

Several important changes happened in the 2025 update:

Software Supply Chain Failures (A03) was introduced to address the growing risk of compromised dependencies.

Mishandling of Exceptional Conditions (A10) was introduced as a brand new concern for 2025.

Security Misconfiguration jumped from #5 to #2, showing how critical proper configuration is.

Server-Side Request Forgery (SSRF) was merged into Broken Access Control.

The list now emphasizes root causes instead of symptoms. For example, instead of "Sensitive Data Exposure" (symptom), it now says "Cryptographic Failures" (root cause).

How to Use This Information

If you're a Developer:

Start learning about these 10 vulnerabilities. Understand how they work and how to prevent them.

Use automated tools like SAST (Static Application Security Testing) to find these vulnerabilities in your code.

Write code with security in mind from the beginning.

If you're in QA or Testing:

Test for these vulnerabilities in applications you're testing.

Run penetration tests focused on these categories.

Report findings to developers with clear explanations.

If you're a Business Owner or Manager:

Ensure your development team is trained on these vulnerabilities.

Implement secure development practices.

Budget for security testing and tools.

Make security part of your culture, not an afterthought.

If you're Just Learning About Security:

This list shows you the most important things to learn about.

Start with #1 (Broken Access Control) and work your way down.

Use free resources like OWASP WebGoat for hands-on learning.

Practice on intentionally vulnerable applications like DVWA or WebGoat.

Conclusion

The OWASP Top 10 2025 shows us that web application security continues to evolve. Traditional code vulnerabilities are still present, but new challenges like supply chain attacks and misconfigurations are becoming increasingly critical.

The good news is that all of these vulnerabilities are preventable. By understanding what they are, how attackers exploit them, and how to defend against them, you can significantly improve your security posture.

Remember: security is not a destination, it's a journey. Keep learning, keep improving, and keep your applications secure.