OWASP Top 10 Explained Simply — With Real Examples
OWASP Top 10 Explained Simply — With Real Examples
TLDR: The OWASP Top 10 is a regularly updated list of the most critical security risks in web applications, maintained by a global non-profit of security researchers. It's not academic — it's a map of the vulnerabilities that attackers actually exploit, in the order they're most likely to find them. If your web application is vulnerable to items on this list, it's a matter of when, not if. Here's what each one means in plain language.
What OWASP Is and Why This List Matters
The Open Worldwide Application Security Project (OWASP) is a non-profit foundation that produces free, openly available security research and tools used by security professionals worldwide. Their Top 10 list — most recently updated in 2021, with a new edition expected in 2025 — is compiled from real vulnerability data across hundreds of organisations and millions of applications.
It matters because it reflects reality. These aren't theoretical risks or edge cases. They're the vulnerabilities that pen testers find in almost every engagement, that appear in almost every breach post-mortem, and that automated scanners are built to detect. If your application is clean against the OWASP Top 10, you've eliminated the vast majority of the attack surface that opportunistic attackers look for first.
Here's each one, explained without the jargon.
The OWASP Top 10, in Plain Language
A01 — Broken Access Control
What it is: Users can access data or functions they shouldn't be allowed to reach.
Real example: You're logged into an app and your profile URL contains user_id=1001. You change it to user_id=1002 and see someone else's private account details. No error. No block. Just their data.
This is the number one vulnerability on the list because it's extraordinarily common and often trivially exploitable. Fixing it requires checking, on the server side, that every request is authorised — not just authenticated.
A02 — Cryptographic Failures
What it is: Sensitive data is stored or transmitted without adequate protection.
Real example: A database breach reveals that user passwords were stored as MD5 hashes — an algorithm so fast that modern GPUs can crack billions of hashes per second. Within hours, the majority of passwords are recovered in plain text.
This covers more than passwords. Unencrypted database fields holding payment data, medical records, or personal information all fall here. The fix is using modern, appropriate encryption standards — bcrypt or Argon2 for passwords, AES-256 for stored data, TLS 1.2+ for data in transit.
A03 — Injection
What it is: Untrusted data is sent to an interpreter — a database, shell, or parser — and treated as a command rather than input.
Real example: A login form accepts ' OR '1'='1 as a username. Because the query is built by concatenating strings, this input rewrites the SQL query and returns all user records, bypassing authentication entirely.
SQL injection is the most well-known variant, but injection extends to OS commands, LDAP queries, XML parsers, and more. Parameterised queries eliminate it at the source.
A04 — Insecure Design
What it is: Security was not considered during the design of a feature, leaving a structural flaw that can't be patched away — only redesigned.
Real example: A password reset flow sends a 6-digit code to a user's email but has no rate limiting on the verification attempts. An attacker can simply try all 1,000,000 combinations automatically until the right code is found.
This is distinct from implementation bugs. The code works exactly as designed. The design itself is the vulnerability. The only fix is rethinking the architecture.
A05 — Security Misconfiguration
What it is: A system is deployed with insecure default settings, unnecessary features enabled, or incomplete hardening.
Real example: A developer deploys a new cloud server and accesses the admin panel to configure it. The credentials are the vendor defaults — admin / admin. The panel has been internet-accessible for three days before anyone notices it was never secured.
This category also covers open cloud storage buckets, verbose error messages in production, and unnecessary services left running on public-facing servers. Misconfiguration is consistently one of the most frequently exploited categories in real-world breaches.
A06 — Vulnerable and Outdated Components
What it is: Your application uses libraries, frameworks, or dependencies with known, unpatched security vulnerabilities.
Real example: A Java application is running a version of a logging library with a critical remote code execution vulnerability. The CVE has been public for weeks. The team hasn't updated yet. An attacker exploits it before they do.
This is exactly what happened with Log4Shell in late 2021 — still one of the most widespread vulnerabilities ever discovered, affecting an enormous proportion of Java-based enterprise software globally. Dependency audits and automated tools like Dependabot are the baseline defence.
A07 — Identification and Authentication Failures
What it is: Flaws in how users are identified, authenticated, or how sessions are managed — allowing attackers to impersonate legitimate users.
Real example: A user logs out of a web application. Their session token remains valid on the server. An attacker who captured that token earlier — through a network intercept or XSS — can continue using it to access the account indefinitely.
This category also covers weak password policies, missing multi-factor authentication on sensitive accounts, and credential stuffing vulnerabilities from no rate limiting on login endpoints.
A08 — Software and Data Integrity Failures
What it is: Code or data is used without verifying that it hasn't been tampered with — often through compromised update pipelines or untrusted plugins.
Real example: An application automatically pulls and executes software updates from a CDN without verifying a cryptographic signature. An attacker who compromises the CDN can push malicious code to every installation simultaneously.
This category gained prominence after the SolarWinds attack in 2020, where a legitimate software update mechanism was compromised to distribute malware to thousands of organisations. Supply chain integrity is now a board-level concern.
A09 — Security Logging and Monitoring Failures
What it is: An application fails to log security-relevant events, or fails to alert when something suspicious is happening — leaving breaches undetected for weeks or months.
Real example: An attacker runs a credential stuffing tool against a login endpoint, attempting 10,000 username/password combinations over 48 hours. No alert fires. No log review catches it. The attacker successfully accesses 200 accounts before anyone notices the spike in failed logins — days later.
The average breach dwell time — the time between compromise and detection — was 194 days in 2024 according to IBM's research. Effective logging and alerting is what closes that gap.
A10 — Server-Side Request Forgery (SSRF)
What it is: An attacker tricks a server into making HTTP requests to internal resources that should never be externally accessible.
Real example: An application accepts a URL as input and fetches the content to display a preview. An attacker submits an internal cloud metadata URL — the kind that AWS, GCP, and Azure expose internally to serve instance credentials. The server fetches it, and the response contains cloud access keys.
SSRF became critical as cloud adoption accelerated. Cloud environments expose internal metadata endpoints that contain sensitive credentials, and SSRF is frequently the path to extracting them.
How to Use the OWASP Top 10 in Your Development Process
The most practical way to use this list is as a review checklist at three points: during design (ask whether each new feature could introduce any of these patterns), during code review (check for injection, access control, and cryptographic issues specifically), and before each major release (run a dependency audit and verify security headers and configurations).
If your team doesn't currently have a formal security touchpoint in your development process, the OWASP Top 10 is the most logical starting framework to build one around. It's free, well-documented, and directly reflects real-world attacker behaviour.
Is Your Application Exposed?
Knowing the list and knowing whether your specific application is vulnerable are two different things. The only reliable way to find out is to test it — either through automated scanning, manual penetration testing, or ideally both.
At Kuboid Secure Layer, our web application assessments are structured around the OWASP Top 10 as a baseline, with deeper testing on the areas most relevant to your stack. If you'd like to understand your current exposure, get in touch — we're happy to have an initial conversation about what a review would involve for your application. You can also explore our full range of security services here.
For more plain-English security guides, visit the Kuboid Secure Layer blog.