Web Security
OWASP Top 10 Vulnerabilities Explained (2026 Edition)
📅 March 9, 2026
⏱️ 10 min read
By VulnScan Security Team
The OWASP Top 10 is the definitive list of the most critical web application security risks. Published by the Open Web Application Security Project (OWASP), it represents broad consensus among security experts about the vulnerabilities that matter most. If your website has any of these issues, you're a prime target for attackers.
A01: Broken Access Control
Broken access control (moved to #1 in 2021) occurs when users can act outside their intended permissions. An attacker can view other users' accounts, modify other users' data, or access unauthorized functionality. This is now the most common vulnerability found in security audits.
Real-world impact: The 2021 Facebook data leak exposed 533 million user records due to broken access control in their phone number lookup feature. Attackers could query the API without rate limiting and extract user data at scale.
How to check: Run VulnScan's free vulnerability scanner to identify broken access control issues on your website in seconds. Our scanner tests for IDOR (Insecure Direct Object References), path traversal, and privilege escalation vectors.
A02: Cryptographic Failures
Previously called "Sensitive Data Exposure," cryptographic failures encompass all failures related to protecting data in transit and at rest. This includes using weak or outdated encryption algorithms, transmitting sensitive data over cleartext protocols, or using hardcoded keys.
Common failures include: MD5 or SHA1 password hashing (easily cracked), HTTP instead of HTTPS, expired or self-signed SSL certificates, and storing credit card numbers in plaintext.
Check your SSL/TLS configuration instantly with our free SSL checker — it identifies weak cipher suites, expired certificates, and missing security headers.
A03: Injection (SQL, XSS, Command)
Injection attacks occur when untrusted data is sent to an interpreter as part of a command or query. SQL injection, XSS (cross-site scripting), and OS command injection are the most common forms. Injection was #1 for 10 consecutive years before dropping to #3 in 2021 — but remains one of the most dangerous vulnerability classes.
SQL injection example: A login form vulnerable to SQL injection lets attackers input `admin' OR '1'='1` and bypass authentication entirely — gaining access to the admin account without knowing the password.
Test your site for SQL injection vulnerabilities and XSS vulnerabilities for free with VulnScan.
A04: Insecure Design
New in the 2021 edition, insecure design refers to missing or ineffective control design — distinct from implementation bugs. Security must be considered from the design phase, not bolted on after. This includes missing threat modeling, no defense-in-depth, and insecure-by-default configurations.
Example: A password reset flow that sends the actual password via email (revealing it's stored in plaintext) represents insecure design. A properly designed system would send a one-time reset link.
A05: Security Misconfiguration
Security misconfiguration is the most common issue in practice. This includes unnecessary features enabled, default accounts unchanged, error messages displaying stack traces, missing HTTP security headers, and cloud storage buckets with public access.
The majority of data breaches involve misconfigured cloud storage (S3 buckets, Azure Blob Storage, Google Cloud Storage). In 2019, Capital One lost 100 million customer records due to a misconfigured AWS Web Application Firewall.
VulnScan's security header checker instantly identifies missing security headers like Content-Security-Policy, X-Frame-Options, HSTS, and more.
A06: Vulnerable and Outdated Components
Using components with known vulnerabilities — outdated libraries, frameworks, plugins — is one of the easiest attack vectors for hackers. This is exactly what Log4Shell (CVE-2021-44228) exploited: millions of systems were vulnerable because they used an outdated version of Apache Log4j.
WordPress sites are particularly vulnerable because of outdated plugins. Check our Log4Shell scanner and WordPress security scanner to identify outdated components.
A07: Identification and Authentication Failures
Previously called "Broken Authentication," this category covers weak session management, missing multifactor authentication, use of weak passwords, and insecure credential storage. Credential stuffing attacks use leaked username/password combinations (from other breaches) to gain access to your site.
Have I Been Pwned tracks over 12 billion compromised credentials. If your users reuse passwords, a breach of any other service becomes a breach of yours.
A08: Software and Data Integrity Failures
New in 2021, this covers assumptions around software updates, critical data, and CI/CD pipelines without verifying integrity. The SolarWinds attack inserted malicious code into a software build pipeline before it was signed and distributed to 18,000 organizations — including US government agencies.
This also includes insecure deserialization, which can lead to remote code execution when an application deserializes attacker-controlled data.
A09: Security Logging and Monitoring Failures
Without adequate logging and monitoring, breaches cannot be detected. The average time to detect a data breach is 197 days. Attackers rely on the absence of monitoring to exfiltrate data over months without detection.
Effective security logging means: logging all authentication attempts, all access control failures, all input validation failures, and having real-time alerts for suspicious patterns.
A10: Server-Side Request Forgery (SSRF)
New as a standalone entry in 2021, SSRF flaws occur when a web application fetches a remote resource based on user-supplied URL. Attackers can force the server to send requests to internal systems behind firewalls — accessing cloud metadata endpoints, internal APIs, or other internal resources.
Capital One was breached via SSRF: an attacker exploited a misconfigured WAF to make the server request the AWS metadata endpoint, revealing IAM credentials that allowed access to S3 buckets containing customer data.
Test for SSRF vulnerabilities with our free SSRF scanner.
Frequently Asked Questions
What is the OWASP Top 10 list?
The OWASP Top 10 is a standard awareness document published by the Open Web Application Security Project, listing the 10 most critical security risks to web applications. It is updated approximately every 3-4 years based on data from security audits and vulnerability reports.
Is OWASP Top 10 compliance mandatory?
The OWASP Top 10 is not a standard or certification — it is a list of awareness documents. However, PCI DSS, SOC 2, and other compliance frameworks reference it. Many security audits and penetration tests use it as a baseline.
What is the most common OWASP vulnerability?
Broken access control is the most common OWASP Top 10 vulnerability found in security audits, appearing in 94% of tested applications according to OWASP's own data. It moved to #1 in the 2021 edition.