Web Application Penetration Testing Explained

Updated March 8, 2025

Having a robust cybersecurity program is essential for any organization. Fortifying defenses and being as proactive as possible in thwarting cyberattacks are standard in the security realm. But how do you know how well you’re doing? To understand this, you need to test your defenses. One of the best ways to do that is with penetration testing.

What Is Web Application Penetration Testing?

Web application penetration testing is a type of ethical hacking where a simulated attack occurs in an attempt to access sensitive data. It assesses the architecture, design, and configuration of your web applications. Web applications include anything delivered over the internet through a browser interface. As a result, they are the most targeted by cybercriminals.

The objective is for you to identify vulnerabilities before hackers do. It’s an essential part of a health check of your systems.

Access Levels for Web Application Penetration Testing

Every penetration test includes a level of access. The three segments are:

• Black Box Penetration Testing: In this scenario, testers don’t know the target system’s internal structure. They play the role of a hacker, seeking to find any weakness to exploit.
• Gray Box Penetration Testing: The test participants have some general information about the target system at this level. They may know about data structures, algorithms, or codes, and they may also have credentials. Penetration objectives here are a bit different and can involve specific test cases to determine the system’s security.
• White Box Penetration Testing: The third option enables pen testers to access systems and artifacts like source code and containers. Additionally, they may be able to enter servers running the system.

Web application testing uses both Black and Gray Box Testing. For a comprehensive view of your system’s security, start with the Black Box and then move to the Gray Box. Here’s how they both work.

Black Box Web Application Penetration Testing

With Black Box, this situation emulates the most realistic hacker experience. The testers put on their hacker hats and copy what an actual cybercriminal would do. Those steps involve reconnaissance, finding vulnerabilities, and breaking into your network. Keep in mind that testers have no context about your system, only URLs.

Gray Box Web Application Penetration Testing

In Gray Box, your partners will test each system in scope. At this point, testers have “user” knowledge and system access. The Gray Box Penetration Test approach focuses on an application with multiple users. It will test authenticated users with various roles to ascertain whether someone could escalate privileges, including:

• Horizontal Privilege Escalation: Tester will attempt, as an authenticated user, to retrieve another user’s data. Someone could potentially do this if the URL is part of the person’s account. For example, you have an application where every user has a unique account number. That account number is part of the URL on the page where the data lives. If you change a number in the URL, the user may be able to obtain entrance into another account.
• Vertical Privilege Escalation: In this exercise, an authenticated user will attempt to assume administrator-level access. A tester could accomplish this if a web application uses a value to represent a username in a hidden field, which returns with successful authentication. A tester would then try to change the value from “username” to “root” or “administrator” to attain that privilege level.

This information provides insight into how a group performs the tests. Another key component of web application pen tests is the OWASP (Open Worldwide Application Security Project) Top 10.

What Is the OWASP Top 10, and Why Does It Matter in Pen Testing?

OWASP is a nonprofit organization that aims to improve software security. Its top 10 is a standard awareness document that developers, cybersecurity professionals, and other security stakeholders can use as a guide. The top 10 is a broad consensus of the most critical risks to web applications. The latest version, from 2021, consists of these categories.

1. Broken Access Control: Access control comes from policies about how a user can operate within an application based on intended permissions. Failures here can cause unauthorized information disclosure, modification, or destruction. The most Common Weakness Enumerations (CWEs) map to this more than any other category.
2. Cryptographic Failures: In this category, you’re looking for how protected data is in transit and at rest, including passwords, PHI (protected health information), intellectual property, data that falls under privacy laws, and credit card numbers.
3. Injection: In Injection, testers would consider an application vulnerable to attack if it doesn’t validate, filter, or sanitize user-supplied data. The application would also check for hostile data.
4. Insecure Design: This was a new category in 2021. It’s a broad category of various weaknesses deemed “missing or ineffective control design.” It focuses on design flaws, not the implementation of the system.
5. Security Misconfiguration: A misconfigured application can be a way in for hackers. As part of the penetration test, testers would look for these signs, such as missing appropriate security hardening, enabling unnecessary features, keeping default accounts and passwords active, handling errors, and more security settings.
6. Vulnerable and Outdated Components: These are known issues that can be difficult to test and discern risk. Testers will locate these risks if they learn that organizations don’t know all the versions they have running, are using unsupported and out-of-date software, haven’t completed fixes or upgrades, or aren’t testing compatibility.
7. Identification and Authentication Failures: Applications should confirm a user’s identity, authentication, and session management. Authentication weaknesses may be present if the application permits credential stuffing, brute force, automated attacks, weak or default passwords, a lack of multifactor authentication, or other authentication failures.
8. Software and Data Integrity Failures: This type of failure refers to code and infrastructure that doesn’t protect against integrity violations. For example, some plugins or modules may be from an untrusted source. If so, there is trouble in the CI/CD (continuous integration/continuous delivery) pipeline. As a result, there could be unauthorized access, malicious code, or system compromise.
9. Security Logging and Monitoring Failures: Most organizations find testing security logging and monitoring challenging. This category focuses on detection, escalation, and response to active breaches. Insufficient activity here can impact your ability to identify and respond.
10. Server-Side Request Forgery (SSRF): An SSRF flaw happens when web applications fetch a remote resource and don’t validate the user-supplied URL. An attacker could manipulate the application to send a crafted response to an unexpected destination, even with firewalls, VPNs, or other barriers in place.

As you can see, the OWASP Top 10 covers a wide range of web application risks. It’s critical that they are part of your pen tests. In addition, there are other common web application issues that your pen test provider should cover. Those categories include different types of injection (e.g., SQL, OS command, server-side code, server-side template, etc.), server-level issues, and other manipulations.

These pen tests are extensive and include seven steps.

The Seven Steps of a Web Application Pen Test

A web application pen test should include these seven phases:

1. Planning and Preparation: Pen-test teams gather information and plot out their attack strategy.
2. Reconnaissance/Discovery: Ethical hackers are investigating and collecting data on the target system. Scanning of systems occurs here.
3. Vulnerability Enumeration/Analysis: Testers conduct a vulnerability assessment to identify weaknesses.
4. Initial Exploitation: After reviewing the results from the assessment, pen testers use techniques to validate, attack, and exploit.
5. Expanding Foothold/Deeper Penetration: After the initial infiltration, testers will strive to go further with escalation.
6. Cleanup: Testing parties retreat from the application and return it to its former state.
7. Report Generation: Your provider creates a comprehensive analysis of the pen tests with details on weaknesses and vulnerabilities as well as remediation recommendations.

Pen tests for your web applications deliver so much valuable information. Let’s look at the benefits of using these.

The Benefits of Web Application Penetration Tests

Penetration testing’s most valuable advantage is that ethical hackers find your weaknesses before the real ones do. It’s a way to improve your cybersecurity measures and be as proactive as possible in thwarting cyberattacks. Additionally, it provides these benefits:

• It can support your compliance program and adherence to regulations. For healthcare organizations, you can exceed the expectations of HIPAA with pen tests.
• You can better assess your infrastructure. Your firewalls and DNS servers are public-facing, and any information adjustments can leave your system vulnerable. Get insights on this before hackers find them.
• You can fix problems within web applications. You may have been unaware of them or not made them a priority. The remediation plan will advise you on what to do.
• It can confirm security policies and if they’re effective.

Ready to realize all these benefits and more? Learn about our web application pen testing services and how we can help today.