OWASP Top 10 Complete Guide to Web Application Security With Easy Examples
Web applications are now used for everything from online shopping and banking to education, healthcare, and business management. Because these applications handle sensitive information, they are common targets for cyberattacks.
The OWASP Top 10 is one of the most widely recognized security awareness resources for web application developers, security professionals, and organizations. It highlights major categories of security risks that can affect web applications.
In this guide, we will explain the OWASP Top 10 in simple language and use a practical real-life example to show how each vulnerability can affect an application.
Note: The OWASP Top 10 is a risk-awareness classification, not a list of ten individual vulnerabilities. OWASP periodically updates it as the application-security landscape changes.
Table of Contents
What Is OWASP?
OWASP stands for Open Worldwide Application Security Project. It is a nonprofit organization that provides free resources, standards, tools, and guidance for improving software and web application security.
OWASP is well known for its OWASP Top 10, which helps organizations understand common and important web application security risks.
What Is the OWASP Top 10?
The OWASP Top 10 is a regularly updated list of major web application security risk categories.
The current major release is OWASP Top 10:2025, which supersedes the 2021 edition. The categories are:
- Broken Access Control
- Security Misconfiguration
- Software Supply Chain Failures
- Cryptographic Failures
- Injection
- Insecure Design
- Authentication Failures
- Software or Data Integrity Failures
- Security Logging and Alerting Failures
- Mishandling of Exceptional Conditions
Let’s understand each one.
1. Broken Access Control
Broken Access Control occurs when an application does not properly restrict what authenticated users are allowed to access or modify.
A user may be able to access another user’s information simply by changing an ID in a URL or manipulating a request.
Example
Imagine an online shopping website has this URL:
A customer is authorized to view order 1001.
The customer changes the URL to:
If the application displays another customer’s order without checking ownership, the application has an access-control vulnerability.
Possible Impact
An attacker could potentially:
- View another user’s personal information
- Modify another user’s data
- Access administrative functions
- Download private documents
- Delete resources they do not own
How to Prevent It
Developers should:
- Perform authorization checks on every protected request
- Never rely only on hidden buttons or UI restrictions
- Verify that the current user owns the requested resource
- Use role-based or attribute-based access control where appropriate
- Test access controls with different user roles
2. Security Misconfiguration
Security Misconfiguration happens when security settings are incorrectly configured, left at insecure defaults, or unnecessarily exposed.
This can occur in the application, web server, database, cloud environment, or framework.
Example
Suppose a company deploys a web application with detailed error messages enabled in production.
When an error occurs, the website displays:
Database connection failed:
mysql://admin:password@example-db/internal
Exposing internal infrastructure or credentials through an error message could give attackers valuable information.
Another example is leaving an administrative interface publicly accessible with default credentials.
Possible Impact
Attackers may discover:
- Database information
- Internal server details
- API keys or credentials
- Debug information
- Administrative interfaces
- Unnecessary services
How to Prevent It
Organizations should:
- Disable debug mode in production
- Remove default accounts and passwords
- Keep servers securely configured
- Disable unnecessary services
- Use secure HTTP headers
- Review cloud and server configurations
- Regularly audit security settings
3. Software Supply Chain Failures
Modern applications rarely consist entirely of code written by the application’s own developers.
They often depend on:
- Open-source libraries
- Frameworks
- Package managers
- Third-party APIs
- Build systems
- Plugins
- Container images
- Development tools
Software Supply Chain Failures occur when weaknesses or compromises in these dependencies or development processes introduce security risks.
Example
Imagine an organization uses a third-party JavaScript package in its application.
The package is compromised after an attacker gains access to the package maintainer’s publishing account. A malicious version is released, and the organization’s automated build process downloads it.
The company’s application could now contain malicious code even though its own developers did not intentionally write it.
Possible Impact
A compromised dependency could lead to:
- Data theft
- Malicious code execution
- Credential theft
- Supply-chain attacks
- Compromised application builds
How to Prevent It
Organizations should:
- Inventory third-party dependencies
- Keep dependencies updated
- Monitor vulnerable packages
- Use trusted package sources
- Protect package publishing credentials
- Review dependency changes
- Secure CI/CD pipelines
- Use software composition analysis where appropriate
4. Cryptographic Failures
Cryptographic Failures occur when sensitive information is not adequately protected through encryption or when cryptography is implemented incorrectly.
This category was previously known as Sensitive Data Exposure in older OWASP Top 10 editions.
Example
Suppose an online education platform stores user passwords using plain text:
username: ali
password: MyPassword123
If an attacker obtains the database, every user’s password is immediately exposed.
A secure application should store passwords using a modern password-hashing algorithm rather than reversible encryption or plain text.
Other Examples
Sensitive information can be exposed when an application:
- Sends confidential data without HTTPS
- Stores passwords in plain text
- Uses weak cryptographic algorithms
- Uses poorly managed encryption keys
- Stores sensitive information unnecessarily
How to Prevent It
Use:
- HTTPS/TLS
- Strong password hashing such as Argon2id or an appropriate modern alternative
- Proper encryption for sensitive data when required
- Secure key management
- Modern cryptographic algorithms
- Data minimization
5. Injection
Injection occurs when untrusted input is interpreted as part of a command or query.
Common examples include:
- SQL injection
- Command injection
- LDAP injection
- NoSQL injection
Example: SQL Injection
Suppose a login system constructs a database query by directly inserting user input:
SELECT * FROM users
WHERE username = ‘USER_INPUT’
AND password = ‘PASSWORD_INPUT’;
If input is not safely handled, an attacker may manipulate the query syntax.
For example, an attacker could attempt to enter specially crafted SQL syntax instead of a normal username.
The resulting query might behave differently from what the developer intended.
Possible Impact
Injection vulnerabilities can potentially allow attackers to:
- Read unauthorized database records
- Modify data
- Delete information
- Bypass application logic
- Execute commands in certain circumstances
How to Prevent It
Developers should use:
- Parameterized queries
- Prepared statements
- Safe ORM/query-builder APIs
- Server-side input validation
- Context-appropriate output encoding
Important: Escaping input alone should not be considered the primary defense against SQL injection when parameterized queries are available.
6. Insecure Design
Insecure Design focuses on security weaknesses caused by flawed application design rather than simply incorrect implementation.
A perfectly coded feature can still be insecure if the underlying business logic was designed without adequate security controls.
Example
Imagine an online banking application allows users to change their account email address.
The design allows:
- User enters a new email.
- Application immediately changes the email.
- No verification is required.
- No notification is sent to the old email address.
An attacker who gains temporary access to the account could change the email address and make account recovery more difficult.
The problem is not necessarily a coding mistake. The security design of the feature is incomplete.
How to Prevent It
Organizations should:
- Perform threat modeling
- Define security requirements before development
- Consider abuse cases
- Design strong authorization workflows
- Add appropriate verification mechanisms
- Apply secure-by-design principles
7. Authentication Failures
Authentication Failures occur when an application does not properly verify a user’s identity or protect authentication mechanisms.
This category includes weaknesses involving:
- Passwords
- Sessions
- Login mechanisms
- Multi-factor authentication
- Account recovery
Example
Suppose a website allows unlimited login attempts:
Username: admin
Password: attempt 1
Password: attempt 2
Password: attempt 3
…
An attacker could repeatedly attempt passwords against an account.
If the password is weak, the account may eventually be compromised.
Other Examples
Authentication weaknesses can include:
- Weak password policies
- Poor session management
- Predictable session identifiers
- Insecure password-reset processes
- Missing MFA for sensitive operations
- Failure to invalidate sessions after important security events
How to Prevent It
Use:
- Strong password hashing
- Multi-factor authentication where appropriate
- Secure session management
- Rate limiting
- Account protection mechanisms
- Secure password-reset workflows
- Reauthentication for sensitive operations
8. Software or Data Integrity Failures
This category concerns applications that trust software, updates, plugins, or critical data without adequately verifying their integrity.
Example
Suppose a company automatically downloads application updates from an external server.
The application installs the update without verifying its authenticity or integrity.
If an attacker compromises the update mechanism, the application could install malicious software.
Other Examples
This can involve:
- Untrusted software updates
- Insecure CI/CD pipelines
- Unsigned or improperly verified packages
- Unsafe deserialization
- Untrusted critical data
How to Prevent It
Organizations should:
- Verify software integrity
- Secure CI/CD systems
- Protect build environments
- Use trusted repositories
- Verify signatures where appropriate
- Restrict who can publish production software
- Monitor changes to critical systems
9. Security Logging and Alerting Failures
Security controls are less effective when an organization cannot detect suspicious activity.
Security Logging and Alerting Failures occur when important security events are not properly recorded, monitored, or alerted on.
Example
Imagine an attacker successfully logs into an administrator account from an unusual location.
The application:
- Does not record the login properly
- Does not generate an alert
- Does not monitor repeated failed login attempts
The attacker can continue operating without attracting attention.
What Should Be Logged?
Depending on the application, security-relevant events may include:
- Login successes and failures
- Password changes
- Privilege changes
- Account recovery events
- Access to sensitive resources
- Administrative actions
- Suspicious input or security violations
How to Prevent It
Organizations should:
- Create useful security logs
- Protect logs from unauthorized modification
- Centralize important logs
- Monitor suspicious activity
- Configure appropriate alerts
- Establish incident-response procedures
Avoid logging sensitive information such as plaintext passwords.
10. Mishandling of Exceptional Conditions
The 2025 OWASP Top 10 includes Mishandling of Exceptional Conditions.
This category covers security problems caused by incorrectly handling unexpected situations such as:
- Errors
- Exceptions
- Resource failures
- Unexpected input
- Invalid states
- Partial failures
Example
Suppose an online payment system processes an order using multiple steps:
- Create order
- Charge payment
- Update inventory
- Mark order as completed
Now imagine the payment succeeds, but the inventory update fails.
If the application does not correctly handle this exceptional condition, it might leave the order in an inconsistent state.
Security problems can arise when error-handling logic accidentally:
- Bypasses authorization
- Exposes sensitive information
- Creates inconsistent security states
- Allows operations that should have been rejected
How to Prevent It
Developers should:
- Handle exceptions securely
- Fail safely
- Use transactions where appropriate
- Avoid exposing internal error details
- Validate application state
- Test failure scenarios
- Ensure security checks remain active during error handling
OWASP Top 10 at a Glance
| OWASP Risk | Simple Meaning | Example |
| Broken Access Control | Users can access things they shouldn’t | Viewing another user’s order |
| Security Misconfiguration | Security settings are incorrectly configured | Production debug mode enabled |
| Software Supply Chain Failures | Dependencies or development systems introduce risk | Compromised package |
| Cryptographic Failures | Sensitive information is inadequately protected | Plaintext passwords |
| Injection | Untrusted input becomes part of a command/query | SQL injection |
| Insecure Design | Security was missing from the feature’s design | Unsafe account recovery design |
| Authentication Failures | Identity verification is weak | Unlimited password attempts |
| Software or Data Integrity Failures | Software/data is trusted without proper integrity verification | Malicious update |
| Security Logging and Alerting Failures | Attacks are not properly detected | Admin compromise produces no alert |
| Mishandling of Exceptional Conditions | Errors and unexpected states are handled insecurely | Payment workflow enters an unsafe state |
A Complete Scenario
Let’s imagine a fictional company called TechShop.
TechShop operates an online shopping platform.
During a security assessment, testers discover several weaknesses.
Problem 1: Broken Access Control
A customer can access another customer’s invoice by changing an order identifier.
Risk: Unauthorized access to personal information.
Problem 2: SQL Injection
The product search functionality builds SQL queries unsafely from user input.
Risk: Unauthorized database access or modification.
Problem 3: Cryptographic Failure
Some sensitive information is stored without adequate protection.
Risk: Data exposure if the database is compromised.
Problem 4: Authentication Failure
The login endpoint does not adequately protect against repeated automated login attempts.
Risk: Increased risk of account compromise.
Problem 5: Logging Failure
The application does not alert administrators about suspicious administrative logins.
Risk: Attackers may remain undetected for longer.
This example shows why application security must be approached as a complete security lifecycle, rather than fixing only one vulnerability.
How Developers Can Use the OWASP Top 10
The OWASP Top 10 can be incorporated into the software development lifecycle.
Step 1: Security Requirements
Identify security requirements before development begins.
For example:
- Users must only access their own data.
- Passwords must never be stored in plaintext.
- Administrative functions require authorization.
- Sensitive communications must use HTTPS.
Step 2: Secure Design
Perform threat modeling and consider how legitimate features could be abused.
Step 3: Secure Development
Developers should use secure programming practices such as:
- Prepared statements
- Strong authentication
- Server-side authorization
- Secure session management
- Input validation
- Safe error handling
Step 4: Security Testing
Test applications using:
- SAST
- DAST
- Dependency scanning
- Manual penetration testing
- Code review
- Configuration reviews
Step 5: Monitoring
After deployment, monitor:
- Authentication events
- Authorization failures
- Application errors
- Suspicious activity
- Security alerts
Step 6: Continuous Improvement
Security is not a one-time task. Applications, dependencies, infrastructure, and threats continuously change.
OWASP Top 10 vs. Penetration Testing
The OWASP Top 10 is a risk-awareness framework, while penetration testing is a security testing activity.
For example:
OWASP Top 10:
Broken Access Control is a major application security risk.
Penetration test:
A tester verifies whether a particular application actually allows one user to access another user’s resources.
Therefore, organizations can use the OWASP Top 10 to guide security testing, but it should not be treated as a complete application-security standard by itself.
Why Is the OWASP Top 10 Important?
Understanding the OWASP Top 10 helps developers and organizations:
- Identify common application security risks
- Build security into software development
- Improve secure coding practices
- Prioritize security testing
- Reduce the likelihood of data breaches
- Improve security awareness
- Communicate application-security risks more effectively
For beginners, it also provides an excellent starting point for learning web application security and ethical hacking.
Final Thoughts
The OWASP Top 10 provides a practical foundation for understanding important web application security risks. From broken access control and injection to cryptographic failures, insecure design, supply-chain risks, and inadequate monitoring, each category represents a class of problems that can have serious consequences.
However, organizations should not treat the OWASP Top 10 as a simple checklist. Effective application security requires secure design, secure coding, testing, configuration management, monitoring, incident response, and continuous improvement.
If you are learning cybersecurity, start by understanding each OWASP category, study vulnerable and secure implementations in an authorized lab, and practice identifying security weaknesses ethically.
Security reminder: Only test applications, systems, and APIs when you have explicit authorization. Never perform penetration testing or vulnerability exploitation against systems you do not own or have permission to assess.
Frequently Asked Questions
What does OWASP stand for?
OWASP stands for Open Worldwide Application Security Project.
What is the OWASP Top 10?
It is a widely used OWASP awareness resource that identifies major categories of web application security risks.
Is the OWASP Top 10 only for ethical hackers?
No. It is useful for developers, security engineers, penetration testers, DevSecOps teams, architects, students, and organizations.
Is OWASP Top 10 a vulnerability scanner?
No. OWASP Top 10 is a risk classification and awareness resource. Tools can help detect some related weaknesses, but no single scanner reliably identifies every issue.
Which programming languages can have OWASP vulnerabilities?
Almost any language or technology used to build web applications can be affected, including PHP, JavaScript, Python, Java, C#, Go, Ruby, and others.
Is OWASP Top 10 enough to secure a website?
No. It is an important foundation, but comprehensive security requires additional controls, testing, secure architecture, monitoring, vulnerability management, and incident response.
