Product Manager at Relevant Software

Your 2023 Guide to Web Application Penetration Testing

January 30, 2023

Due to the growing number of cyber threats, companies are constantly looking for new ways to protect their web apps. Web application penetration testing is one of those techniques, and it has already become an essential part of any solid protection strategy.

The popularity of penetration testing, also known as Pen Test or Pen Testing, is constantly growing. According to Markets and Markets, the pen testing market is expected to increase from $1.7 billion in 2020 to $4.5 billion by 2025. That’s why in this article, we suggest discovering what penetration testing for a web application is, why it is important, and what protective value it adds.

What Is Web Application Penetration Testing?

A Pen Test, as the name suggests, is a test that focuses solely on a web application and not on a whole network or company. Penetration testing for web applications is carried out by initiating simulated attacks, both internally and externally, to get access to sensitive data.

A web penetration testing allows us to determine any security weakness of the entire web application and across its components, including the source code, database, and back-end network). This helps the developer prioritize the pinpointed web app vulnerabilities and threats as well as come up with strategies to mitigate them.

Why Is Web Application Penetration Testing Important? 

Penetration testing is at the forefront of the software development lifecycle, a proactive sentinel tirelessly working to expose the unseen vulnerabilities in a web application. Its importance cannot be overstated in an age where digital threats are not just commonplace but continually evolving.

H3: Identifying Vulnerabilities

Imagine a fortified castle. It appears impenetrable, but there could be a hidden passage or a weak stone unbeknownst to the dwellers. Identifying vulnerabilities in a web application is much the same. It’s about unearthing those hidden passages and reinforcing the weak stones before a malicious entity can exploit them.

Penetration testing plays a pivotal role in exposing security flaws before they become a playground for attackers. It is like a treasure hunt, where the treasure is the potential weaknesses, and the hunters are the ethical hackers striving to find these treasures before the pirates do. In doing so, they are not just protecting the integrity of the application but are guardians of user trust and data security.

The value of user data is immense in the digital world, and safeguarding it is not just a matter of trust but of ethical responsibility. By identifying and addressing vulnerabilities, organizations build robust digital fortresses that maintain user trust and protect against the reputational damage that accompanies security breaches.

H3: Compliance and Legal Requirements

More than merely bolstering online defenses, penetration testing plays a crucial role as a guide through the intricate web of legalities and compliance responsibilities. Numerous norms and benchmarks, especially the General Data Protection Regulation (GDPR) and the Health Insurance Portability and Accountability Act (HIPAA), mandate a scrupulous defense of user information by organizations.

Meeting compliance is far from a simplistic administrative task; it represents the fostering of a dependable digital persona. Deviating from these norms results not only in reputational damage but also brings about substantial monetary fines and legal repercussions. The undertaking of penetration testing is analogous to a seafaring vessel undergoing extensive scrutiny prior to setting sail. This scrutiny assures that the ship is capable of weathering the unpredictable waters of the digital universe and securely delivering its prized contents—user data.

Navigating deftly through the digital sphere and avoiding legal obstacles becomes attainable for organizations by ensuring adherence through penetration testing. This strategy highlights a firm commitment to safeguarding users, thereby establishing the entity as a pillar of reliability within the boundless digital landscape.

web application penetration testing

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Types of Penetration Testing for Web Applications

You can pen-test web applications in two ways: by simulating an inside or an outside attack. Let’s look at how these different types of attacks are designed and carried out:

Method 1: Internal Pen Testing

As the name implies, the internal penetration testing of web applications is performed within the organization via LAN (local area network), including testing web applications that are hosted on the intranet.

This facilitates the identification of any vulnerabilities that may exist within the corporate firewall. One of the greatest misconceptions is that attacks can only occur externally, so sometimes, one can undervalue the importance of internal web penetration testing.

Some of the internal attacks that can happen include: 

  • Malicious Employee Attacks by aggrieved employees, contractors, or other parties who have resigned but still have access to the internal security policies and passwords;
  • Social Engineering Attacks trick people into giving up information or performing certain actions to gain control over sensitive information, such as usernames, passwords, or banking credentials;
  • Phishing Attacks are also a type of social engineering attack, but in this case, an attacker sends an email with a malicious link that looks like an authentical one;
  • Attacks using User Privileges typically occur when an attacker has gained access to a user’s account, either by stealing or cracking their password.

The pentest is done by trying to access the environment without valid credentials and determining the possible route of attacks. 

Method 2: External Pen Testing

Unlike internal pen tests, external pen testing focuses on attacks initiated from outside the organization to test web applications hosted on the Internet.

Testers, also called ethical hackers, do not have information about the internal system and the security layers implemented by the organization. They were simply given the IP address of the target system to simulate external attacks.

No other information is given, and it is up to the testers to search public web pages to get more information about the target host, infiltrate it, and compromise it. External pen testing includes testing the organization’s firewalls, servers, and IDS. 

Web Application Penetration Testing Methodology

Penetration testing methodology implies four phases which are cyclic. The testers repeat them until no vulnerabilities are found. Let’s discover them in brief. 

web application penetration testing roadmap
  • Recon. The first phase in testing is reconnaissance, which is the process of gathering information about the target to be tested. 
  • Mapping. Once you have your targets’ names and IP addresses, you must map out their network topology. Such application threat modeling involves understanding how different networks are connected together and what kind of security controls they have in place.
  • Discovery. After mapping out the target’s network, you need to discover any vulnerabilities that could allow an attacker to gain access to sensitive data. 
  • Exploitation. This means creating exploits like SQL injections or buffer overflows and using them to gain access to sensitive information within the system itself.

How is Penetration Testing for Web Apps Done? 

Pen testing for web apps focuses on the environment and the setup process instead of the app itself to do it. This involves gathering information about the target web app, mapping out the network that hosts it, and investigating the possible points of injection or tampering attacks. 

Here are the steps involved in web app penetration testing: 

Step 1: Active and Passive Reconnaissance

The first step in web app pen testing is the reconnaissance or information-gathering phase. This step provides the tester with information that can be used to identify and exploit vulnerabilities in the web app. 

Passive reconnaissance means collecting information available on the internet without directly engaging with the target system. This is mostly done using Google, beginning with subdomains, links, previous versions, etc.

Active reconnaissance, on the other hand, means directly probing the target system to get an output. Here are some examples of methodologies used for active reconnaissance:

  • Nmap Fingerprinting. You can use the Nmap network scanner to get information about the web app’s scripting language, OS of the server, server software and version, open ports, and services currently running. 
  • Shodan Network Scanner. This tool can help you get additional information that is publicly available about the web app, including geolocation, server software used, port numbers opened, and more. 
  • DNS Forward And Reverse Lookup. This method allows you to associate the recently discovered subdomains with their respective IP addresses. You can also use Burp Suite to automate this process. 
  • DNS Zone Transfer. You can do this by using the nslookup command to find out the DNS servers being used. Another option would be to use DNS server identification websites, then use the dig command to attempt the DNS zone transfer.
  • Identify Related External Sites. This part of the information-gathering phase is important because of the traffic that flows between the external websites and the target website. Using the Burp Suite covers this step quite easily. 
  • Analyze HEAD and OPTION Requests. The responses generated from HEAD and OPTIONS HTTP requests show the web server software and its version, plus other more valuable data. You can use Burp Suite’s intercept on feature when visiting the target website to get this information. 
  • Data From Error Pages. Error pages provide more information than you’d expect. By modifying the URL of your target website and forcing a 404 Not Found error, you’ll be able to know the server and the version the website is running on.
  • Checking the Source Code. Examining the source code helps you find helpful information you can use to pinpoint some vulnerabilities. It helps you determine the environment the app is running on and other relevant information. 
  • Documenting All Data. After getting all this information, it is important to organize and document your findings, which you can use later on as a baseline for further study or for finding vulnerabilities to exploit. 

Step 2: Attacks or Execution Phase

The next step is the actual exploitation step. In this phase, you implement the attacks based on the information you have gathered during the reconnaissance stage. 

There are several web application penetration testing tools you can use for the attacks, and this is where data gathering plays an important role. The information you collect will help you narrow down the tools that you need based on the research you’ve done so far

Step 3: Reporting And Recommendations

After the data collection and exploitation processes, the next step is to write the web application pen testing report. At this point, a cybersecurity developer creates a concise structure for your report and makes sure that all findings are supported by data. Aside from writing down the successful exploits, the developers have to categorize them by criticality to deal with the more serious exploits first. 

Web Application Penetration Testing Tools

Web application penetration testing tools are a vital part of any organization’s security strategy. These tools simulate attacks on a web application in order to identify vulnerabilities and assess the effectiveness of the application’s defenses. Let’s look at the top penetration tools used for web applications in the industry today: 

web application penetration testing tools

John The Ripper

John the Ripper is a popular tool for penetration testing. It can be used to perform dictionary attacks on passwords, as well as brute-force attacks. It works by taking a text file containing usernames and passwords and then launching an attack on each one. It then tells you if the password was found or not and how many times it tried to crack it.


SQLmap is a tool for penetration testing that helps you execute SQL injection attacks. It’s a command line-based tool that automates the process of detecting and exploiting SQL injection flaws and was designed to be fast, efficient, and free. It can be used against any type of SQL injection vulnerability, including blind and error-based injection.


Wireshark is one of the most popular network protocol analyzers right now, facilitating deep inspection of protocols, as well as live-traffic capture and offline analysis of a captured file. The data can be exported using XML, PostScript, CSV, or plain text format for documentation and further analysis. 


This vulnerability scanner helps testers identify vulnerabilities, configuration problems, and even the presence of malware on web applications. This tool, however, is not designed for executing exploitations but offers great help when doing reconnaissance. 


Nmap or Network Mapper is more than a scanning and reconnaissance tool. It is used for both network discovery and security auditing purposes. Aside from providing basic information on the target website, it also includes a scripting module that can be used for vulnerability and backdoor detection and execution of exploitations. 


Metasploit stands out among other penetration testing tools for web applications. The reason is that this is actually a framework and not a specific application. You can use it to create custom tools for particular tasks. You can use Metasploit to:

  • Select and configure the exploit to be targeted
  • Select and configure the payload to be used
  • Select and configure the encoding schema 
  • Execute the exploit


Aircrack-ng is a wireless LAN tool that can be used to recover WEP/WPA/WPA2 keys. It’s one of the most popular wireless hacking tools, and it has been around since 2002. It’s used by penetration testers to test the security of wireless networks and find weaknesses, but it also comes with a few other use cases, including:

  • Identifying networks that are not properly secured
  • Cracking open Wi-Fi hotspots with weak passwords or no encryption at all
  • Decrypting traffic on encrypted Wi-Fi networks

Burp Suite

We’ve mentioned Burp Suite a couple of times earlier, and this is because this tool is an all-in-one platform for testing the security of web applications. It has several tools that can be used for every phase of the testing process, including Intercepting proxy, Application-aware spider, Advanced web application scanner, Intruder tool, Repeater tool, and Sequencer tool. 

Penetration Testing Certifications

Although the concept of penetration testing seems simple at first glance, building a career in this field requires specific certifications. Let’s review them in brief. 

Certified Ethical Hacker (CEH) certification

CEH is a vendor-neutral, professional certification demonstrating a candidate’s ability to analyze and test computer networks for security weaknesses. The CEH credential requires candidates to pass an exam that tests their knowledge of network security, scanning, and testing. The certification also requires candidates to demonstrate their ability to use hacking tools in an ethical manner.

GIAC Exploit Researcher and Advanced Penetration Tester (GXPN)

GIAC Exploit Researcher and Advanced Penetration Tester (GXPN) is an advanced certification that focuses on the core skill set of a penetration tester. The GXPN certification validates the tester’s ability to perform advanced penetration tests, research exploits, and develop custom exploits. 

GIAC Penetration Tester (GPEN) certification

The GIAC Penetration Tester (GPEN) certification is a globally recognized credential that proves a tester has the skills to perform advanced penetration testing. The GPEN certification tests your ability to analyze and interpret data; perform vulnerability analysis; identify risks associated with vulnerabilities; create test plans and execute them; implement security measures to protect against attacks; and use common tools and techniques.

Licensed Penetration Tester Master (LPT) Certification

The Licensed Penetration Tester Master (LPT) Certification is a rigorous, two-year program that will teach you everything you need to know about penetration testing. This certification is designed to give a tester the skills and knowledge necessary to perform an in-depth analysis of networks and systems, as well as develop strategies for protecting valuable data and assets.

Offensive Security Certified Professional (OSCP)

Offensive Security Certified Professional (OSCP) is a professional certification in the field of penetration testing. It was created by Offensive Security and offers a comprehensive course for security professionals to prepare for the OSCP certification exam. The OSCP certification is aimed at penetration testers who are looking to gain the skills needed to perform advanced penetration tests and operate in high-risk environments.

Automated vs. Manual Pentesting

Automated and manual web application penetration testing are two different approaches to conducting a penetration test.

Automated pen testing involves using specialized software tools to scan a system for vulnerabilities and perform attacks. This approach is fast and efficient, and it can cover a large number of vulnerabilities in a short amount of time. However, it can also produce false positives (i.e., reporting vulnerabilities that do not actually exist) and may not be able to identify all vulnerabilities, especially those that require a human touch to discover.

Manual pen testing, on the other hand, involves a skilled security professional manually testing a system for vulnerabilities and exploiting them. This approach is slower and requires more human effort, but it can be more thorough and accurate. Manual pen testing can uncover vulnerabilities that automated tools might miss, and it allows the tester to think creatively and adapt to unexpected situations.

While both approaches have pros and cons, they can be used together successfully to create a more thorough test. In fact, some companies find that combining the two approaches gives them the best possible results by bringing together the strengths of each method.

Read our guides on how to hire a cybersecurity developer and site reliability engineer

Web Application Penetration Testing: Summing Up 

Web applications are convenient, cost-effective, and value-adding. However, most systems are publicly exposed to the Internet, and the data can become easily available to those who are willing to do a bit of research. What’s more, even the most advanced web applications are prone to vulnerabilities, in both design and configuration, that hackers might find and exploit. Because of this, the web application penetration testing roadmap should be a priority.

Relevant has helped more than 200 companies with setting up teams of remote developers and site reliability engineers with industry-specific expertise and a product-oriented mindset. Our cybersecurity developers would also be glad to help you run a web application penetration testing and get an insightful look into the possible vulnerabilities. 

Contact us now to get a quote for penetration testing for your web app. 

et a quote for penetration testing for your web app. 


Written by
Product Manager at Relevant Software
For more than 6 years, I've been working as Business Analyst and Product Manager at Relevant. I'm responsible for requirements engineering and management and solution implementation control.

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