Navigating the OWASP Top 10

In an era where cyber threats evolve faster than ever, staying ahead of vulnerabilities is crucial for developers, security professionals, and organizations alike. The Open Web Application Security Project (OWASP) has been a beacon in this landscape since 2001, providing free, open-source resources to bolster application security. Their flagship "Top 10" lists serve as essential guides, highlighting the most critical risks based on real-world data and expert insights. As we navigate 2025, with the recent release candidate for OWASP Top 10 2025 sparking discussions, it's the perfect time to explore the methodologies behind these lists. This article dives into the OWASP Top 10 2021 and 2017 for web applications, alongside the OWASP Mobile Top 10 2024, uncovering their purposes, categories, comparisons, strengths, weaknesses, and key takeaways.

Today, OWASP serves as a standard for assessing security risks in software code.

Evolution of Security Risks in Web and Mobile Apps

At its core, the OWASP Top 10 aims to educate and empower. These lists aren't exhaustive checklists but awareness tools designed to prioritize the most prevalent and impactful security risks. By focusing on the "top 10," OWASP encourages developers to integrate security from the design phase, often referred to as "shifting left", reducing breach risks and compliance headaches. For web apps, the 2017 and 2021 editions reflect the shift from opinion-based rankings to data-driven insights, drawing from hundreds of thousands of applications. The Mobile Top 10 2024, meanwhile, addresses the unique challenges of mobile ecosystems, like device-specific threats and supply chain vulnerabilities. Together, they foster a proactive security culture, enabling teams to mitigate risks that could lead to data leaks, financial losses, or reputational damage in our increasingly interconnected world.

Explanation of the Three Methodologies

Each OWASP Top 10 methodology evolves from its predecessors, adapting to technological advancements and emerging threats. Let's break them down.

• OWASP Top 10 2017 (Bridging Opinion and Data):  The 2017 version, released after a four-year gap, was a hybrid model: about 60% community-driven via surveys of over 2,000 experts and 40% data from 40,000 apps. It introduced risk ratings combining prevalence, detectability, exploitability, and impacts, merging categories to reduce overlap. This transitional methodology highlighted the rise of DevOps and microservices, adding entries like Insufficient Logging to address underreported issues, while still relying on consensus for balance.
• OWASP Top 10 2021 (A Data-Driven Revolution):  Released in September 2021, this edition marked a pivotal shift toward empirical evidence. Drawing from over 500,000 applications and 13 data contributors, it uses a rigorous methodology emphasizing incidence rates, exploited prevalence, and weighted exploit/impact scores from Common Weakness Enumerations (CWEs). Community surveys serve only as tiebreakers for low-data risks. This approach consolidated categories, introduced new ones like Insecure Design, and renamed others for clarity, reflecting real-world exploits in modern architectures like APIs and cloud services.
• OWASP Mobile Top 10 2024 (Tailored for Mobility):  Updated in 2024 after an eight-year hiatus, this list focuses on mobile-specific risks, sourced from vulnerability databases, incident reports, and assessments. It aligns with the OWASP Mobile Application Security Verification Standard (MASVS), using criteria like occurrence frequency, exploitation likelihood, and trend analysis. Emphasizing defense-in-depth, it tackles modern threats like supply chain attacks and runtime protections in iOS and Android ecosystems.

The Evolution of AppSec Risk: List of Categories

Each methodology lists groups of vulnerabilities into 10 categories, mapped to CWEs, with descriptions, impacts, and mitigations. Here's a concise overview.

OWASP Top 10 2017 Categories

• [A1] Injection: Similar to 2021, focusing on code injection.
• [A2] Broken Authentication: Session and credential mishandling.
• [A3] Sensitive Data Exposure: Unprotected data at rest or in transit.
• [A4] XML External Entities (XXE): XML parsing vulnerabilities.
• [A5] Broken Access Control: Unauthorized function access.
• [A6] Security Misconfiguration: Default or error-prone settings.
• [A7] Cross-Site Scripting (XSS): Script injection into web pages.
• [A8] Insecure Deserialization: Manipulated object data.
• [A9] Using Components with Known Vulnerabilities: Outdated dependencies.
• [A10] Insufficient Logging & Monitoring: Poor incident response capabilities.

OWASP Top 10 2021 Categories

• [A1] Broken Access Control: Failures in enforcing user permissions, leading to unauthorized access.
• [A2] Cryptographic Failures: Weak encryption exposing sensitive data.
• [A3] Injection: Malicious input executed as code, like SQL injection.
• [A4] Insecure Design: Fundamental flaws in architecture.
• [A5] Security Misconfiguration: Improper setups enabling exploits.
• [A6] Vulnerable and Outdated Components: Unpatched libraries with known issues.
• [A7] Identification and Authentication Failures: Weak login mechanisms.
• [A8] Software and Data Integrity Failures: Unverified updates or deserialization risks.
• [A9] Security Logging and Monitoring Failures: Inadequate detection of breaches.
• [A10] Server-Side Request Forgery (SSRF): Apps tricked into accessing unauthorized resources.

OWASP Mobile Top 10 2024 Categories

• [M1] Improper Credential Usage: Hardcoded or mishandled credentials.
• [M2] Inadequate Supply Chain Security: Risks from third-party components.
• [M3] Insecure Authentication/Authorization: Weak mobile auth flows.
• [M4] Insufficient Input/Output Validation: Data tampering opportunities.
• [M5] Insecure Communication: Unencrypted data transmission.
• [M6] Inadequate Privacy Controls: Over-collection or mishandling of user data.
• [M7] Insufficient Binary Protections: Easy reverse engineering.
• [M8] Security Misconfiguration: App settings exposing vulnerabilities.
• [M9] Insecure Data Storage: Unsafe storage on devices.
• [M10] Insufficient Cryptography: Weak encryption in mobile contexts.

Comparison of the Three OWASP Methodologies

While all three aim to prioritize risks, their scopes and approaches differ significantly.

The 2021 version refines 2017's hybrid model into a more objective framework, while the Mobile 2024 stands apart by tailoring to device ecosystems, incorporating unique factors like binary protections absent in web lists.

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Strengths and Weaknesses

OWASP Top 10 2017

• Strengths: Balanced expert insights for underrepresented issues; easy to understand for beginners.
• Weaknesses: Heavier reliance on surveys introduces subjectivity; smaller dataset limits accuracy in fast-evolving threat landscapes.

OWASP Top 10 2021

• Strengths: Highly empirical, transparent datasets on GitHub, better reflects modern exploits like SSRF. Promotes "secure by design."
• Weaknesses: Still underrepresents process risks (e.g., design flaws) due to automation biases; may overlook emerging threats without sufficient data.

OWASP Mobile Top 10 2024

• Strengths: Mobile-specific, aligns with standards like MASVS; highlights trends like supply chains amid rising app attacks.
• Weaknesses: Less frequent updates (last in 2016); platform variances (iOS vs. Android) can complicate universal application.

Security Isn't a One-time Fix

The OWASP Top 10 methodologies are indispensable roadmaps in the fight against cyber vulnerabilities, evolving from opinion-led lists to data-centric guides that adapt to web and mobile realities. While the 2017 edition laid the groundwork, 2021's rigor sets the stage for innovations like the 2025 release candidate, which introduces new data and risks while keeping staples like Broken Access Control at #1. For mobile, the 2024 list reminds us that as apps become ubiquitous, so do their unique perils. Ultimately, these tools underscore a timeless truth: security isn't a one-time fix but an ongoing commitment. Developers, audit your code using tools like SonarQube, and stay vigilant. In the digital frontier of 2025, knowledge is your strongest defense.

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Want to know more? Watch our YouTube video,  TOP 10 Data Privacy Threads, to learn more about the latest developments.

Pictures / Logos from pixabay.com, OWASP,  and NUCIDA Group
Article written and published by Torsten Zimmermann