The Complete Checklist to Web App Pentest (OWASP Top 10)

Modern apps power your business, but they also expose it to attackers. Penetration testing helps identify vulnerabilities before attackers could exploit web applications. 

In this blog, we will discuss OWASP top 10 risks and a comprehensive web application penetration testing checklist to effectively test web applications against the OWASP Top 10 security risks.

Understanding OWASP Top 10 Risks

The OWASP Top 10 outlines the most critical security risks to web applications. It serves as an essential guide for developers and security professionals to understand and mitigate the most common vulnerabilities in web applications.

The list is updated every four years. It was last updated in 2021 and the next release is planned in 2025. Security experts use the OWASP Top 10 list to prioritize their security efforts and ensure their web applications are secure. 

The updated OWASP Top 10 vulnerabilities of 2021 witnessed some significant changes with new threats such as insecure design, software, and data integrity failures, and server-side request forgery rising to secure spots amongst the top 10 most critical vulnerabilities of the year.

These updates have made the list a more comprehensive framework for the security of web applications, helping security experts identify and address vulnerabilities more effectively.

A01: Broken Access Control

Staying at #1 in 2025, Broken Access Control remains the most common and damaging issue. It happens when systems don’t properly restrict what users can do, letting them access data or actions they shouldn’t. This often comes from missing permission checks, weak backend validation, or trusting the frontend too much.

A02: Security Misconfiguration

Moving up to #2, Security Misconfiguration reflects how small setup mistakes can create large security gaps. Things like open cloud storage, unused services, default credentials, or missed patches are easy to overlook but easy to exploit. As infrastructure becomes more complex, these configuration slips have become one of the most common real-world attack paths.

A03: Software Supply Chain Failures

Now ranked #3, Software Supply Chain Failures focus on risks introduced through third-party libraries, build tools, and deployment pipelines. Attackers use trusted components to slip in malicious code. Because these dependencies are widely reused, a single compromise can quietly impact thousands of systems at once.

A04: Cryptographic Failures

Holding the #4 spot, Cryptographic Failures happen when sensitive data isn’t protected the right way. This includes weak encryption, poor key handling, or data sent without encryption at all. When cryptography is misused or skipped, attackers can easily intercept credentials or personal information meant to stay private.

A05: Injection

Dropping to #5, Injection vulnerabilities appear when applications treat user input as commands. Attackers exploit this by injecting malicious code into databases or browsers. These issues usually come from weak input validation and unsafe query handling, and they can quickly lead to data leaks or full system compromise.

A06: Insecure Design

Insecure Design points to problems baked into the system from the start. These aren’t coding mistakes but design-level gaps—like missing trust boundaries or unsafe assumptions. When security isn’t part of early planning, fixing these issues later often requires redesigning entire workflows.

A07: Authentication Failures

Authentication Failures occur when systems can’t reliably confirm who a user is. Weak passwords, missing multi-factor authentication, or flawed login flows make it easier for attackers to take over accounts. These issues often enable credential stuffing or session hijacking without triggering alarms.

A08: Software or Data Integrity Failures

This has held its position at #8, this category covers cases where software or data is trusted without proper verification. Unsigned updates, compromised dependencies, or tampered build pipelines can introduce malicious code silently. Because these sources appear legitimate, attacks often spread widely before anyone notices something is wrong.

A09: Security Logging and Alerting Failures

Staying at #9, this risk comes from poor visibility into what’s happening inside systems. When logs are missing or alerts aren’t monitored, attacks can go unnoticed for long periods. Without reliable records, teams struggle to detect breaches or understand what actually went wrong.

A10: Mishandling of Exceptional Conditions

It focuses on how systems behave when something goes wrong. Poor error handling, missing validations, or unsafe fallback logic can expose internal details or break workflows. Attackers often exploit these edge cases to bypass controls or trigger unexpected behavior.

Want to explore these risks in more detail? This deep dive into OWASP Top 10 Security Risks, 2025 explains how they show up in real-world applications.

Web Application Penetration Testing Checklist

Without any further delay, let us dive into the web application penetration checklist to conduct a thorough web app penetration testing:

1. Information Gathering:

• Go through the application manually. Visit every page and use all available features to understand how it works and how users interact with it.
• Use a spidering or crawling tool like Burp Suite or OWASP ZAP to discover hidden files, directories, and pages that aren’t directly linked.
• Look for exposed files such as robots.txt, sitemap.xml, or .DS_Store. These often reveal unlisted paths or internal information that should not be public.
• Check cached or archived pages using Google Cache or the Wayback Machine. These may contain old or sensitive content that has since been removed from the live site.
• Identify the technologies behind the site—frameworks, server software, and specific libraries. Use HTTP headers, JavaScript files, and fingerprinting tools to gather this data.
• List all input points, such as forms, file upload fields, and API endpoints. Intercept their requests using tools to understand how data is sent and handled.
• Look for business logic issues, unused API calls, or any hardcoded credentials or tokens.
• Create test accounts to simulate different user roles, and compare what each role can see or do. This helps uncover broken or missing access controls.

2. Configuration Management: 

• Confirm that the web server does not support resource manipulation methods from the internet (such as PUT and DELETE).
• Determine whether the site is virtually hosted, as additional sites may be vulnerable and could compromise the base server.
• Verify that known vulnerabilities with available vendor patches are not present.
• Make sure no backup files of source code are available on the public-facing part of the application.
• Address common web server configuration issues, such as directory listings and leftover sample files.
• Check that web server components like FrontPage Server Extensions or Apache modules do not introduce security vulnerabilities.
• Detect the presence of common directories within the application root (such as /backup and /admin).
• Check for language or application defaults, such as environmental quirks or the availability of default files and loaded modules.
• Ensure that administrative interfaces to infrastructure components (e.g., web servers, application servers) are not accessible from the internet.
• Ensure that administrative interfaces to the application itself are not publicly exposed.

3. Authentication:

• Verify that usernames and passwords are transmitted over an encrypted channel.
• Check for default account names and passwords still in use.
• Avoid using public identifiers like email addresses or SSNs as usernames.
• Enforce password complexity to make brute-force or guessing attacks difficult.
• Prevent passwords from being sent to users via email.
• Lock user accounts temporarily after a set number of failed login attempts.
• Avoid using special meta characters in passwords. 

4. Access Control: 

• Make sure access control rules are enforced correctly.
• Users should not be able to gain unauthorized access or unlock hidden features by modifying inputs, query strings, cookies, or JavaScript values.
• Verify that every protected resource performs a proper authorization check before it is displayed to the user.
• After logging in, test whether a user can manipulate session data—like user IDs or account numbers—to access or act on another person’s account.
• Try visiting protected pages directly, either without logging in or by bypassing the login screen. These pages should be completely inaccessible without valid authentication.
• Some applications follow a strict sequence of actions, such as during checkout or account setup. Confirm that users cannot skip steps or jump ahead by tampering with requests.

5. Authorization: 

• Check for path traversal by entering payloads like ../, %2e%2e/, or ..\\ in input fields that handle file names or paths.
• Try accessing sensitive files such as to confirm whether directory access is properly restricted
• Attempt to bypass authorization by modifying roles or parameters in the request.
• Test whether valid tokens or session cookies from one user can be reused in another session.
• Look for horizontal access control flaws by changing IDs in requests. 
• Try visiting internal or restricted routes without logging in to verify that unauthorized access is blocked.
• Every sensitive endpoint or API must enforce both authentication and proper permission checks on the server side.

6. Session Management:

• Disable HTTP methods like PUT and DELETE on the web server unless they are explicitly required.
• Check if the application is virtually hosted. Other sites sharing the same server could be vulnerable and pose a risk to the main application.
• Ensure all software and components are fully patched and up to date.
• Look for backup copies of source code (e.g., .bak, .zip, .old) that may have been accidentally left in publicly accessible directories.
• Fix any web server misconfigurations, including disabling directory listings and removing default files or sample content.
• Review server components such as Apache modules or legacy tools like FrontPage Server Extensions for potential vulnerabilities.
• Check for sensitive directories like /backup, /admin, or /test, which are often overlooked and may expose configuration files or credentials.
• Restrict access to all administrative panels and infrastructure tools.

7. Error Handling:

• Trigger various errors (e.g., invalid input, broken URLs, forced exceptions) and observe how the application responds.
• Verify that error messages do not expose stack traces, database dumps, or internal system details.
• Return only generic error messages to users, while logging detailed errors securely for administrative access.
• Check whether the application returns different responses for an invalid username versus an incorrect password (e.g., “User does not exist” vs. “Password incorrect”).
• Confirm that all authentication failures return a single, generic message such as “Invalid username or password” to avoid leaking information about user accounts.

8. Data Protection:

• Check that no sensitive data is rendered in visible form fields.
• Verify browser caching is disabled for sensitive pages.
• Confirm all stored data is encrypted.
• Verify only secure SSL/TLS versions (TLS 1.2 or higher) are enabled.
• Disable SSL 2.0, SSL 3.0, TLS 1.0, and TLS 1.1.
• Ensure all anonymous key exchange methods (e.g., ADH) are disabled.
• Remove support for RC2, DES, and other weak algorithms.
• Confirm encryption key length is at least 128 bits.
• Validate that encryption keys are securely stored and rotated.
• Confirm the digital certificate is signed by a trusted CA.

9. Input Validation:

• Prevent any part of the application from executing scripts included in user input.
• Reject SQL commands submitted through user input to protect against SQL injection.
• Block execution of operating system commands originating from user-supplied data.
• Disallow processing of LDAP commands provided by users.
• Sanitize all inputs to prevent storage or reflection of malicious script code.

10. Buffer Overflow

• Protect the application from any buffer overflow vulnerabilities.
• Safeguard the application against heap overflow conditions.
• Prevent the application from being susceptible to stack overflows.
• Eliminate the risk of format string overflows within the application.

Bottomline

Testing web applications for security issues helps catch problems early, before they become serious. Fixing weak spots in login systems, session handling, and data flow lowers the risk of data leaks. 

Doing regular checks and controlled attacks keeps the system ready for new types of threats. When teams follow clear security steps and stay alert, they protect both users and the business. If you are interested to know more about our penetration testing services, reach out to us.

References resources: 

OWASP Penetration Testing Check List

OWASP Web Security Testing Guide | OWASP Foundation

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