Web Application Penetration Testing Case Study

Web Application Penetration Testing Case Study

Client Profile

Industry: Business Services
Company Size: Mid-Market
Assessment: Web Application Penetration Testing
Testing Approach: Authenticated and Unauthenticated Testing
Methodology: OWASP-aligned penetration testing
Primary Objective: Identify vulnerabilities that could lead to unauthorized access, data exposure, or compromise of business-critical application functionality

Client information has been removed to protect confidentiality.

The Challenge

The client used a key web application to help customers and employees manage daily business tasks. This app handled sensitive information and gave users access to features based on their roles and permissions.

Like most applications, the platform had evolved over time and had taken on different forms.

Over time, new features were added, user roles changed, and integrations and APIs were built to connect with other systems. The application became the main part of the company’s daily work.

The company’s leadership team wanted to answer a straightforward question:

Could an attacker compromise the application or gain access to information they were not supposed to see?

The company had standard security controls in place and kept up with development. Still, automated scans and routine checks could not match the confidence that comes from having a skilled security team try to break business logic or get into the application.

The company engaged Tanner Security to perform an independent web application penetration test.

The Objective

The primary objective of the engagement was to identify vulnerabilities that could realistically be exploited by an external attacker or an authenticated user in a gray-box testing approach.

Instead of just running an automated scanner and listing possible issues, Tanner Security tested how the application would respond to real-world attacks.

Our team focused on several important areas of application security, including authentication, authorization, session management, input validation, access controls, business logic, and the application’s handling of sensitive information.

The testing also evaluated whether hidden vulnerabilities could be combined to create a more serious attack path, which is often left out of automated tests.

A vulnerability that seems minor on its own can become much more serious when combined with another weakness.

How the Web Application Penetration Test Worked

Tanner Security began the engagement by working with the client’s team to establish the testing scope and objectives.

This included identifying the applications and functionality to be assessed, defining authorized testing boundaries, determining appropriate user roles and credentials, and identifying systems that should not be affected by testing.

Clear scoping is key for any penetration test. It lets our team test thoroughly while keeping production systems and business operations safe.

Tanner Security’s web application penetration testing methodology includes planning and scoping, reconnaissance, vulnerability assessment, exploitation, post-exploitation, and privilege escalation, followed by detailed reporting and remediation recommendations.

Reconnaissance and Application Mapping

The assessment began with reconnaissance and information gathering.

Our team examined the application’s publicly accessible functionality and identified potential entry points, technologies, authentication mechanisms, APIs, user roles, and other components that could be relevant to an attack.

This step helps testers see the application the way an attacker would.

The goal is not just to see what the application is meant to do.

It’s also about understanding how someone might use it in ways the original developers did not expect.

Automated Scanning and Manual Testing

Automated security tools are used and can be extremely useful during a web application penetration test, particularly for identifying common vulnerabilities and areas that require additional investigation.

But automated scanning is just one part of our web app pen tests.

This difference was especially important during this specific pen test, since some parts of the application required testers to see how different functions worked together.

Automated tools can identify technical weaknesses , but experienced testers can figure out if those weaknesses could actually be used in a real attack.

Authentication Testing

Our pen testing team evaluated the application’s authentication to determine whether unauthorized users could bypass or weaken the login process.

Testing included reviewing authentication workflows, session behavior, password-related controls, and other mechanisms used to establish a user’s identity.

Authentication is one of the first security boundaries protecting a web application.

If someone can get past that first barrier, the rest of the application’s security controls may not work as well.

Authorization and Privilege Escalation Testing

One of the most important areas of the assessment involved authorization.

Authentication answers the question:

“Who are you?”

Authorization answers:

“What are you allowed to do?”

A user may successfully authenticate to an application but still attempt to access information belonging to another user or perform administrative functions that should be restricted.

The testing team evaluated whether users could access functionality or information outside their assigned permissions.

This included testing different user roles and attempting to identify opportunities for horizontal and vertical privilege escalation.

Horizontal privilege escalation happens when one user can access another user’s information or functionality.

Vertical privilege escalation occurs when a lower-privileged user can get access to functions intended for a higher-privileged user or administrator.

These vulnerabilities are especially serious because they could let someone with a real account see information they should not have access to.

Input Validation and Injection Testing

Tanner’s web app penetration tests also review how the application processes user-submitted information.

Web applications frequently accept input through login forms, search fields, account management functions, APIs, file uploads, and other interfaces.

If the application does not check and handle input correctly, attackers might be able to change how it works.

Testing included evaluating the application for common injection risks and other input-handling weaknesses, including SQL injection and cross-site scripting.

Tanner Security’s web application penetration testing services specifically address vulnerabilities such as SQL injection, cross-site scripting, broken authentication, and privilege escalation.

Session Management Testing

A secure login process is only part of authentication security.

Once a user logs in, the application must securely manage the user’s session.

The web application penetration test examined how sessions were created, maintained, and terminated.

Our pen testing team evaluated whether weaknesses in session management could allow an attacker to take over another user’s session or maintain access after a user should have been logged out.

Session management is often missed because the app can seem secure when logging in normally.

Penetration testing checks what happens if someone tries to trick or break that process.

Business Logic Testing

Technical vulnerabilities are not the only concern.

Web applications usually contain complex business processes that automated tools cannot fully understand.

For example, an application may require a user to complete several steps before performing an important transaction.

A web app pen tester can attempt to manipulate that workflow by skipping steps, changing the order of operations, repeating requests, modifying parameters, cookies, or performing actions using an account that should not have access.

These are often referred to as business logic vulnerabilities.

These issues can be hard to spot because the software might be working exactly as it was designed, which is why our team spends so much time tracking them down and attempting to break them.

The Findings

This particular web app pen test identified security weaknesses that required remediation.

Rather than simply providing the client with a long list of technical issues, our team evaluated each finding for exploitability, severity, potential impact, and the application’s business context.

This difference matters for executives.

A report with dozens of vulnerabilities does not always show leaders which problems are most important.

A useful penetration test should help answer:

• Which findings should we fix first?
• What could an attacker actually accomplish?
• What information or systems could be affected?
• How difficult would exploitation be?
• What security improvements would provide the greatest reduction in risk?

Tanner Security’s reports give clear details about each vulnerability, how severe it is, what impact it could have, and what steps to take to fix it.

Remediation and Retesting

Following the penetration test, the client received a detailed report documenting the vulnerabilities identified and the recommended remediation steps.

The development and IT teams could then decide which fixes to tackle first based on risk.

This is one of the major differences between a penetration test and an automated vulnerability scan.

A vulnerability scanner may tell you that a potential weakness exists.

A penetration test can demonstrate how that weakness could be exploited and what an attacker might accomplish.

After fixing the issues, companies can benefit from focused retesting to make sure the main vulnerabilities have been resolved.

The Result

The web app pen test gave this particular client the evidence security tools alone could not offer.

Instead of assuming the application’s security controls were working as intended, the company had an independent security team actively attempting to defeat them.

The engagement helped the client identify weaknesses before they could be discovered and exploited by an unauthorized attacker.

More importantly, the findings gave the development and security teams a clear plan for improving application security.

Key Lessons From the Engagement

A Vulnerability Scan Is Not a Penetration Test

Automated vulnerability scanning is useful in a cybersecurity assessment, but it cannot replace penetration testing.

A scanner identifies potential vulnerabilities.

A penetration tester investigates vulnerabilities, attempts to exploit them, evaluates attack paths, and determines the potential consequences of a successful compromise.

For web applications, this difference is especially important because many serious weaknesses involve how the app works, handles permissions, or connects different parts together.

Authentication Is Only the Beginning

Just having a secure login page does not mean the whole application is secure.

Once a user gains access, the application must enforce appropriate authorization across all functions.

Testing authenticated users is therefore an important component of many web application penetration tests.

Tanner Security also offers authenticated web application penetration testing to evaluate what a legitimate user or an attacker with compromised credentials could access after logging in.

Custom Applications Require Custom Testing

Businesses increasingly rely on applications developed specifically for their needs.

These applications may include proprietary business logic, APIs, cloud integrations, mobile interfaces, third-party services, and complex user roles.

This complexity can lead to vulnerabilities that basic automated scans might miss.

Tanner Security’s web application penetration testing services specifically address these types of environments through manual testing of application functionality, business logic, APIs, user roles, and integrations. Learn more about the difference between a custom application pen test and a web application pen test. 

When Should a Business Perform a Web Application Penetration Test?

A web application penetration test should be considered whenever an application handles sensitive information, performs important business functions, processes financial transactions, provides customer access, represents a significant part of the company’s digital infrastructure, or may be used for compliance requirements.

Testing is especially valuable before launching a new application or a major update.

Businesses should also consider testing after significant application changes, acquisitions, major architecture changes, or security incidents.

For companies subject to regulatory or contractual requirements, penetration testing may also be part of an ongoing compliance program.

Tanner Security’s web application penetration testing services can support security and compliance efforts involving frameworks and requirements such as PCI, HIPAA, ISO 27001, NIST, and CIS.

Web Application Penetration Testing vs. Vulnerability Scanning

These two services work well together but are not the same.

A vulnerability assessment primarily uses automated technologies to identify known weaknesses.

A web application penetration test takes a more active approach.

The tester attempts to exploit vulnerabilities, manipulate application functionality, bypass controls, escalate privileges, and determine how individual weaknesses could be combined into a larger attack.

For a business wanting to know if a web application is truly secure, this difference is important.

A vulnerability scan can tell you where to look.

A penetration test helps determine what an attacker could actually do.

Why Tanner Security?

Tanner Security approaches web application penetration testing from the perspective of a real-world attacker.

The assessment combines automated tools with manual testing and evaluates more than just a list of known vulnerabilities.

The team examines authentication, authorization, input validation, session management, application functionality, privilege escalation, and other attack paths that could result in unauthorized access or data exposure.

The result is a detailed report that helps both technical teams and business leaders understand what was found, why it matters, and what to do next.

Web Application Penetration Testing FAQs

What is a web application penetration test?

A web application penetration test is a simulated attack against a web application designed to identify vulnerabilities that could be exploited by real attackers. Testing may evaluate authentication, authorization, session management, input validation, business logic, APIs, and other application components.

What vulnerabilities can a web application penetration test identify?

Depending on the application, testing can identify SQL injection, cross-site scripting, broken authentication, authorization weaknesses, privilege escalation, session management vulnerabilities, insecure APIs, business logic flaws, and other security weaknesses.

Is a web application penetration test the same as a vulnerability scan?

No. A vulnerability scan primarily uses automated tools to identify potential vulnerabilities. Penetration testing combines automated scanning with manual analysis and controlled exploitation to determine whether vulnerabilities can actually be used to compromise the application.

Should web application penetration testing be authenticated?

Authenticated testing is often valuable because it allows testers to evaluate what users can access after logging in. It can uncover authorization problems, privilege escalation, insecure functionality, and data exposure that may not be visible to an unauthenticated tester.

Does web application penetration testing follow OWASP?

A professional web application penetration test commonly uses OWASP guidance as part of its methodology. Tanner Security offers OWASP penetration testing designed to evaluate applications against critical web application security risks.

How often should a company perform web application penetration testing?

The appropriate frequency depends on the application’s risk, rate of development, regulatory requirements, and business importance. Many businesses perform testing annually and additionally after significant application changes, major releases, or security incidents.

Does penetration testing damage the application?

Testing should be carefully scoped and controlled to minimize operational impact. Before testing begins, the tester and client should establish authorized targets, testing windows, prohibited activities, and procedures for handling unexpected issues.

How much does web application penetration testing cost?

Cost depends on application complexity, the number of applications, user roles, APIs, functionality, environments, and the depth of required testing. A simple application generally requires less testing effort than a large custom platform with multiple integrations and complex business logic.

What happens after a penetration test?

The business receives a report documenting the findings, severity, potential impact, evidence, and recommended remediation. After significant issues are corrected, retesting can be performed to verify that the vulnerabilities have been addressed.

Web Application Penetration Testing Conclusion

A web application might look secure from the outside but still have vulnerabilities that an experienced attacker could exploit.

That is why penetration testing is important.

The purpose is not just to find as many vulnerabilities as possible. The real goal of a web app pen test is to see how an attacker could use the application, what controls they could get around, what information they could access, and what the business impact would be.

For companies that use web applications to serve customers, process transactions, manage sensitive data, or support key operations, an independent penetration test provides valuable evidence of whether those systems can withstand a real-world attack.

If your business depends on a web application, the real question is not whether you think it is secure.

It’s whether you’ve tested it.