Security is not solely the responsibility of the cybersecurity team. In reality, just a small mistake in the source code — a loosely controlled checkpoint, or a poorly filtered statement — is enough for attackers to exploit and cause serious impact on the entire system. That is why identifying and preventing vulnerabilities right from the design and web application development stage is something that cannot be overlooked.
To support developers, testers, and technical experts in approaching security in a more systematic and effective way, the OWASP organization was founded. With the mission of raising awareness and providing open-source standards for web application security, OWASP has be
1. What is OWASP?
OWASP (short for Open Web Application Security Project) is an international non-profit organization specializing in web application security. It may sound a bit “academic,” but simply put, OWASP is an open community — where experts, software engineers, and security researchers come together to share knowledge, tools, and resources to help developers write safer code and protect applications from common vulnerabilities.
What makes OWASP special is that all the resources and tools they provide are free and publicly available. Anyone — whether a student, developer, or security professional — can access, learn, and apply them in real-world work.
Some of OWASP’s notable projects
- OWASP Top 10: A list of the 10 most common security vulnerabilities in web applications. This is very well-known, and almost anyone working with the web should be familiar with it.
- OWASP ZAP: An open-source security testing tool that helps detect vulnerabilities in websites.
- Cheat Sheets: Concise, practical guides that help developers write more secure code with ease.
Why is OWASP important to you?
If you are a developer, then OWASP is like a reliable companion — always reminding you of common mistakes, pointing out potential risks, and more importantly, helping you build code that not only runs well but is also safe for users. After all, nothing is worse than having the application you built become a gateway for attackers to harm others.
And if you are an ordinary user, you might not know what OWASP is — but thanks to the standards set by OWASP, the things you do every day, such as shopping online, logging into your bank account, or simply reading the news on a website, are quietly being protected behind the scenes. OWASP may not stand out on the user interface, but it plays a vital role in making the digital world you live in a little safer every day.
Having established its importance, next let’s review the 10 most common vulnerabilities today to understand their mechanisms and how to remediate them. Let’s get started…!!!
2. OWASP Top 10 – The most common security vulnerabilities list
OWASP Top 10 is a document that summarizes the ten most common and critical security vulnerabilities in web applications, updated regularly based on real-world data from hundreds of security organizations. The OWASP Top 10 is not just a list. It is a wake-up call for anyone working with the web — from backend developers to testers, sysadmins, and security researchers. Below, I will dive into each vulnerability, explaining its mechanism, real-world impact, and sustainable prevention methods.
The latest OWASP Top 10 version (2021) includes:
1. Injection (SQL Injection, Command Injection…)
Risk: Hackers inject malicious SQL statements into input fields such as search boxes or login forms. For example: entering ' OR 1=1 -- into the password field can cause the system to bypass authentication and grant unauthorized access.
Consequence: Hackers can read, modify, or delete sensitive data in the database.
Prevention:
- Use ORM (Object-Relational Mapping) such as Django ORM instead of writing raw SQL queries manually.
- Use prepared statements or parameterized queries.
- Validate, filter, and sanitize invalid input data.
2. Cross-Site Scripting (XSS)
Risk: Hackers inject malicious JavaScript code into comments, forms, or URLs. When other users access the page, this code executes and steals cookies, login information, etc.
Consequence: Users may have their accounts hijacked; the website may be injected with malicious or inappropriate content.
Prevention:
- Encode all data displayed to HTML.
- Do not allow users to inject HTML/JS code (or use a whitelist if necessary).
- Use a Content Security Policy (CSP) to restrict which scripts are allowed to run.
3. Broken Authentication
Risk:
- Credential stuffing: using leaked account/password pairs to perform automated login attempts.
- Brute-force: attempting thousands of random passwords until the correct one is found.
Consequence: Attackers can gain access to admin or user accounts.
Prevention:
- Use strong password hashing algorithms (bcrypt, argon2).
- Apply login attempt limits, CAPTCHA, and two-factor authentication (2FA).
- Always regenerate the session ID after login.
4. Insecure Deserialization
Risk: Hackers send serialized data containing malicious code. When the system deserializes it without proper validation, the malicious code gets executed.
Consequence: Attackers may execute remote code (Remote Code Execution).
Prevention
- Do not deserialize data received from the client unless it has been strictly validated.
- Use safe data formats such as JSON instead of binary formats or pickle.
- Apply digital signatures or encryption to validate data.
5. Sensitive Data Exposure
Risk: Hackers steal data because the system stores or transmits it without encryption (HTTP instead of HTTPS, passwords stored in plain text, etc.).
Consequence: Leakage of personal information, financial data, and user passwords.
Prevention:
- Always use HTTPS (TLS) to encrypt connections.
- Passwords must be hashed and salted with strong algorithms.
- Do not log sensitive information to the console or files.
6. Security Misconfiguration
Risk: Hackers discover leaked sensitive information such as detailed error messages, .env files, or unrestricted access to admin pages.
Consequence: Hackers may identify weaknesses to access the system or take control of it.
Prevention:
- Disable debug mode in the production environment.
- Restrict access permissions to critical files.
- Enforce strict authentication for admin pages and APIs.
7. Broken Access Control
Risk: Hackers modify URLs or requests to access resources they are not authorized for. For example: changing /user/123/edit to /user/124/edit.
Consequence: Unauthorized access to other users’ data or manipulation of the system.
Prevention:
- Validate access permissions on the server side (not just on the frontend).
- Each request must revalidate the user’s role.
- Do not trust data from the client (cookies, sessions, forms, etc.).
8. Directory Traversal / File Upload Vulnerabilities
Risk: Changing the uploaded file name to ../../../etc/passwd to access system files, or uploading a shell script to gain remote access.
Consequence: Gaining control over the server or stealing data.
Prevention:
- Restrict the types of files allowed for upload.
- Rename stored files to avoid duplication or execution.
- Verify the actual MIME type and file extension.
- Do not allow direct access to the upload directory.
9. Security Logging and Monitoring Failures
Risk: Attackers perform a series of actions such as password guessing, SQLi/XSS attacks, uploading malicious code, etc. If the system does not log activities or send early warnings, these actions can quietly occur over a long period without being detected.
Consequence: Hackers gain more time to exploit systems, take admin control, steal data, etc., without the technical team knowing until the damage occurs.
Prevention:
- Keep comprehensive and detailed logs:
- Protect logs from unauthorized modification or access:
- Integrate a monitoring system (SIEM).
- Enable real-time alerting.
Regularly test logs
10. Server-Side Request Forgery (SSRF – Server-side request spoofing)
Risk:
Assume the system has a feature to preview images from a URL. An attacker supplies a URL such as http://127.0.0.1:8080/admin, causing the server to request internal content. From there the attacker can:
- Retrieve internal information (AWS metadata, database configuration…)
Send requests to exploit vulnerabilities in other internal systems
- Perform cross-attacks between the server and the internal network.
Consequence: Unauthorized access to internal systems, theft of sensitive information, or remote takeover of the server.
Prevention:
Restrict the destination URLs that requests can be sent to.
- Block access to internal IP addresses.
- Use an internal firewall or proxy.
- Do not blindly process responses from internal services.
- Regularly update third-party libraries.
3. Practical Application of OWASP in Software Development
OWASP is not just a list of vulnerabilities – it is a guideline for building secure, sustainable, and reliable software. Applying OWASP resources and recommendations at every stage of software development can significantly reduce security risks and help ensure compliance with international standards.
Applying OWASP in the software development phase
| Phase | Applying OWASP |
| Requirements & Analysis | Use OWASP ASVS (Application Security Verification Standard) to define security requirements from the outset. |
| Design | Apply OWASP Threat Modeling to analyze threats and design systems to defend against them. |
| Programming | Follow OWASP Secure Coding Practices to prevent vulnerabilities such as SQL Injection, XSS, and more. |
| Testing | Use OWASP ZAP (Zed Attack Proxy) to perform both automated and manual application security testing. |
| Deployment | Follow the hardening steps in the OWASP Deployment Guide to secure the production environment. |
| Maintenance | Monitor vulnerabilities using OWASP Dependency-Check and update software regularly. |
Practical OWASP Support Tools
| Resources | Description | Application |
| OWASP Top 10 | OWASP’s most prominent document, listing the 10 most common security threats to web applications. | Used by businesses, developers, and security professionals as a standard for security testing and training. |
| OWASP ASVS (Application Security Verification Standard) | A set of security assessment standards at multiple levels, designed for web applications and APIs. | Useful for guiding systematic security testing, especially when developing software with a Security by Design approach. |
| OWASP Testing Guide | A comprehensive guide on how to perform web application security testing. | An essential reference for pentesters and QA professionals who want to integrate security testing into the development process. |
| OWASP ZAP (Zed Attack Proxy) | An open-source tool for both automated and manual security testing. | Easy to use, free, and suitable for both beginners and experts. ZAP can be integrated into CI/CD pipelines for automated security testing. |
| OWASP Cheat Sheet Series | A concise, practical guide covering specific security topics such as Authentication, Session Management, HTTPS Configuration, SQL Injection, and more. | Short and easy to understand, ideal for quickly finding standardized solutions to security issues. |
| OWASP Security Knowledge Framework (SKF) | A learning platform that provides secure coding guidance with practical examples. | Highly suitable for internal training, security staff education, or learning secure coding practices. |
| OWASP Dependency-Check | A tool for checking third-party libraries for known security vulnerabilities. | Very useful when using popular packages like npm, pip, Maven, etc., and wanting to ensure they have no known vulnerabilities. |
| OWASP CycloneDX | A standard format for creating an SBOM (Software Bill of Materials – a list of software components). | Used in DevSecOps to manage software supply chain risks. |
| OWASP CSRFGuard / AntiSamy / ESAPI | Libraries that help protect applications against specific attack types such as CSRF, XSS, and Injection. | Easy to integrate into Java applications and ready to use immediately. |
4. Common Mistakes When Applying OWASP
Although OWASP resources are an effective guide for building secure systems, many individuals and organizations still make serious mistakes during implementation. Here are the most common errors:
1. Focusing only on the Top 10 and neglecting other OWASP projects
- Misunderstanding: Many people think that simply protecting against the OWASP Top 10 is enough to ensure security.
- Reality: OWASP provides many resources such as ASVS (Application Security Verification Standard), Security Knowledge Framework, Cheat Sheets Series, etc. — all of which are very useful for building a comprehensive secure system.
- Consequence: Missing out on advanced standards and security-by-design guidance.
2. Using OWASP as a fixed checklist
- Misunderstanding: Some security teams treat the Top 10 as a checklist that must be fully ticked off during testing.
- Reality: The OWASP Top 10 is a risk guidance framework, not a complete checklist for every system.
- Consequence: Potentially overlooking vulnerabilities specific to the architecture, programming language, or industry in use.
3. Applying it mechanically without analyzing actual risks
- Misunderstanding: Some organizations apply OWASP rigidly, without assessing which threats are truly relevant to their system environment.
- Reality: Effective security must be considered within the real-world context, including the data being processed, target users, and system architecture.
- Consequence: Wasting time patching low-impact vulnerabilities while overlooking potentially serious ones.
4. Failing to update to new versions
- Misunderstanding: Using older OWASP Top 10 versions, such as 2013 or 2017, without updating to the latest 2021 content.
- Reality: OWASP regularly updates its lists in response to technological developments and emerging threats.
- Consequence: Accidentally overlooking new risks such as Software and Data Integrity Failures (added in the 2021 version).
5. Assigning tasks only to the security team without integrating into the development process (SDLC)
- Misunderstanding: Believing that security is solely the responsibility of the security team.
- Reality: OWASP encourages integrating security throughout the entire development process (DevSecOps).
- Consequence: Development teams lack security knowledge, resulting in code that is prone to vulnerabilities.
6. Lack of training for developers
- Misunderstanding: Assuming that having automated scanning tools is sufficient.
- Fact: OWASP provides a variety of specialized training materials for developers (e.g., OWASP Juice Shop, Cheat Sheets).
- Consequence: Developers repeat the same mistakes because they do not fully understand the root cause.
5. Conclusion
Web application security is no longer optional, but a mandatory factor in today’s digital era. Through OWASP and the OWASP Top 10 list, developers, security experts, and businesses alike can identify and mitigate the greatest risks within their systems.
Understanding and applying OWASP standards not only makes your application more secure, but also demonstrates professionalism and responsibility in the software development process.
6. References:
- Official OWASP Website: [https://owasp.org](https://owasp.org)
- OWASP Top 10 (latest version): https://owasp.org/Top10/
- OWASP Web Security Testing Guide: https://owasp.org/www-project-web-security-testing-guide/
- OWASP Application Security Verification Standard (ASVS): https://owasp.org/www-project-application-security-verification-standard/
- OWASP Cheat Sheet Series: https://cheatsheetseries.owasp.org/
