# OWASP Top 10 Web Application Security
The OWASP Top 10 represents the consensus view of the most critical security risks to web applications, compiled and maintained by the Open Web Application Security Project (OWASP). This list serves as the de facto standard for web application security awareness across the cybersecurity industry, providing organizations with a foundational understanding of the most prevalent and impactful vulnerabilities affecting modern web applications.
OWASP updates this list approximately every three to four years based on comprehensive data analysis from security firms, bug bounty platforms, and organizations worldwide. The methodology combines quantitative data on vulnerability frequency with qualitative assessment of exploitability, detectability, and business impact. This evidence-based approach ensures the Top 10 reflects real-world threat patterns rather than theoretical concerns.
The list exists to bridge the gap between complex security research and practical application security needs. Development teams, security professionals, and business leaders use it as a starting point for risk assessment, secure coding practices, and security testing programs. Unlike technical vulnerability databases such as the Common Vulnerabilities and Exposures (CVE) system, the OWASP Top 10 focuses on categories of weaknesses that consistently cause the most significant damage to organizations.
The Top 10 fits within the broader application security ecosystem as a high-level guidance document. It complements more detailed frameworks like the OWASP Application Security Verification Standard (ASVS) and testing guides by identifying priority areas for security investment and attention.
The OWASP Top 10 operates as a categorization system that groups related vulnerabilities under broader risk categories. Each category in the 2021 edition addresses fundamental weaknesses in how web applications handle security controls, process data, or manage user interactions.
Broken Access Control (A01) encompasses failures in enforcing user permissions and restrictions. This includes vertical privilege escalation (accessing admin functions as a regular user), horizontal privilege escalation (accessing other users' data), and direct object references without authorization checks. A common example involves web applications that rely solely on client-side controls to hide administrative features, allowing attackers to directly access admin URLs.
Cryptographic Failures (A02) covers inadequate protection of sensitive data through weak or missing encryption. This includes using deprecated algorithms like MD5 for password hashing, transmitting sensitive data over unencrypted connections, or storing encryption keys alongside encrypted data. Many applications fail by implementing custom cryptographic solutions rather than using established, peer-reviewed libraries.
Injection (A03) occurs when untrusted data gets sent to interpreters as part of commands or queries. SQL injection remains the most recognized subtype, where malicious SQL code manipulates database queries. Cross-Site Scripting (XSS) represents another form where malicious scripts execute in users' browsers. Command injection allows attackers to execute system commands on the host operating system.
Insecure Design (A04) represents a new category focusing on risks from flawed architecture and design patterns. Unlike implementation bugs, these issues stem from missing or ineffective security controls in the application's fundamental design. Examples include applications that lack rate limiting, fail to segregate tenant data in multi-tenant systems, or implement business logic that cannot be secured through coding practices alone.
Security Misconfiguration (A05) addresses the gap between secure software and secure deployment. Default configurations often prioritize functionality over security, leaving unnecessary features enabled, default credentials unchanged, or verbose error messages exposed. Cloud storage buckets misconfigured for public access represent a modern example of this category.
Vulnerable and Outdated Components (A06) reflects the reality that modern applications incorporate numerous third-party libraries, frameworks, and dependencies. Organizations often lack visibility into these components, their versions, and associated vulnerabilities. The 2017 Equifax breach exemplified this risk when attackers exploited a known vulnerability in the Apache Struts framework.
Identification and Authentication Failures (A07) covers weaknesses in identity verification and session management. Weak password policies, missing multi-factor authentication, and improper session handling enable various attack vectors. Credential stuffing attacks succeed because applications fail to detect and prevent automated login attempts using compromised credentials.
Software and Data Integrity Failures (A08) addresses risks from insecure CI/CD pipelines, auto-updates, and object deserialization. Applications that automatically download updates without signature verification or accept serialized objects from untrusted sources create pathways for code execution attacks.
Security Logging and Monitoring Failures (A09) encompasses insufficient visibility into application security events. Without adequate logging, organizations cannot detect attacks in progress, investigate incidents effectively, or demonstrate compliance with regulatory requirements.
Server-Side Request Forgery (SSRF) (A10) occurs when applications fetch remote resources without validating user-supplied URLs. Attackers can use this to access internal systems, cloud metadata services, or perform port scanning from the application server's perspective.
The business impact of OWASP Top 10 vulnerabilities extends far beyond technical systems to affect revenue, reputation, and regulatory compliance. Organizations that ignore these fundamental security risks face consequences that can threaten their operational viability and market position.
Data breaches resulting from these vulnerabilities carry direct financial costs averaging $4.35 million globally according to IBM's 2022 Cost of a Data Breach Report. However, the total business impact encompasses regulatory fines, legal settlements, remediation costs, and lost business opportunities. The Equifax breach, which exploited a vulnerable component (A06), resulted in settlements exceeding $700 million and ongoing reputational damage.
Regulatory frameworks increasingly reference the OWASP Top 10 as a baseline for adequate security measures. The Payment Card Industry Data Security Standard (PCI DSS) explicitly requires protection against common vulnerabilities, while the European Union's General Data Protection Regulation (GDPR) mandates appropriate technical measures that implicitly include addressing these fundamental risks. Organizations that suffer breaches due to unpatched known vulnerabilities face higher regulatory scrutiny and penalties.
Operational disruption represents another significant impact. Injection attacks can corrupt or destroy data, requiring expensive restoration processes and potentially causing extended downtime. Broken access control can compromise entire customer databases, necessitating customer notification, credit monitoring services, and extensive forensic investigation.
The interconnected nature of modern business amplifies these impacts. Third-party partners, suppliers, and customers may terminate relationships following security incidents, creating cascading business effects. Organizations in regulated industries like healthcare and finance face additional scrutiny that can affect licensing and operational permissions.
A common misconception suggests that compliance frameworks or penetration testing alone address OWASP Top 10 risks. While these activities provide value, they often focus on point-in-time assessments rather than the continuous security practices necessary to prevent these fundamental vulnerabilities. Another misconception assumes that web application firewalls (WAFs) or similar perimeter controls provide complete protection. These tools offer defense-in-depth value but cannot substitute for secure application development practices.
Organizations also underestimate the skill level required to exploit these vulnerabilities. Automated scanning tools and exploit frameworks have lowered the barrier to entry, enabling less sophisticated attackers to identify and exploit common weaknesses at scale.
Within the Continuous Defense Architecture framework, the OWASP Top 10 falls primarily under the Vulnerability Surface Domain (VSD), which focuses on identifying and eliminating exploitable weaknesses in systems and applications. The VSD approach recognizes that web application vulnerabilities represent persistent attack surfaces that require systematic reduction rather than reactive patching.
CDA's Continuous Surface Reduction (CSR) methodology directly addresses OWASP Top 10 risks through the principle "Every surface you expose is a surface we eliminate." Rather than accepting these vulnerabilities as inevitable consequences of web development, CSR drives organizations to fundamentally reduce their exposure through architectural and procedural changes.
This approach differs significantly from conventional application security programs that focus primarily on vulnerability identification and remediation. Traditional programs create cycles of discovery and patching that never fully eliminate risk, as new vulnerabilities continuously emerge from ongoing development activities. CSR breaks this cycle by eliminating entire categories of risk through design decisions and automation.
For example, addressing injection vulnerabilities through CSR involves eliminating dynamic query construction rather than implementing input validation. Organizations adopt parameterized queries, stored procedures, and object-relational mapping frameworks that make injection technically impossible rather than attempting to filter malicious input. This approach eliminates the attack surface rather than defending it.
Security misconfiguration receives similar treatment through infrastructure as code and immutable deployment practices. Rather than securing configurations post-deployment, CSR embeds security controls into automated deployment pipelines that eliminate the possibility of manual misconfiguration. Container technologies and serverless architectures further reduce configuration attack surfaces by abstracting infrastructure management.
The VSD methodology emphasizes measurement and continuous improvement of surface reduction efforts. Organizations track metrics such as the percentage of applications using secure frameworks, the elimination of legacy authentication systems, and the adoption of secure-by-default configurations. These metrics provide quantitative evidence of attack surface reduction rather than relying on vulnerability counts or assessment scores.
CDA's approach also integrates OWASP Top 10 considerations into the broader defense architecture rather than treating application security as an isolated domain. The Attack Surface Domain (ASD) maps how web application vulnerabilities interact with network exposure and system access paths. The Control Surface Domain (CSD) ensures that security controls addressing these vulnerabilities integrate effectively with overall security operations.
• The OWASP Top 10 represents data-driven consensus on the most critical web application security risks, updated every three to four years based on real-world vulnerability and exploit data.
• These vulnerabilities cause significant business impact including regulatory fines, data breach costs, operational disruption, and reputational damage that can threaten organizational viability.
• Modern attack tools and frameworks have lowered the skill barrier for exploiting these common vulnerabilities, making them accessible to less sophisticated threat actors.
• Effective mitigation requires architectural and design changes that eliminate attack surfaces rather than relying solely on detection, monitoring, or perimeter controls.
• The 2021 edition introduces "Insecure Design" as a distinct category, recognizing that some security risks cannot be solved through implementation fixes and require fundamental architectural changes.
• Web Application Firewalls: Implementation and Limitations • Secure Code Review: Automated and Manual Techniques • Vulnerability Management: Enterprise Program Development • DevSecOps: Security Integration in Development Pipelines • Penetration Testing: Web Application Assessment Methods
• OWASP Foundation. "OWASP Top 10 2021." Open Web Application Security Project, 2021. https://owasp.org/Top10/
• National Institute of Standards and Technology. "SP 800-53 Rev. 5: Security and Privacy Controls for Federal Information Systems and Organizations." NIST, September 2020.
• MITRE Corporation. "Common Weakness Enumeration (CWE) Top 25 Most Dangerous Software Weaknesses." MITRE, 2021.
• International Organization for Standardization. "ISO/IEC 27034-1:2011 Information technology — Security techniques — Application security." ISO, 2011.
• SANS Institute. "CWE/SANS TOP 25 Most Dangerous Software Errors." SANS, 2021.