Web Applications Penetration Testing: A Pentest Guide

Web applications are targeted by attacks every day - from simple scanners to deliberate breaches. To understand how vulnerable a web application is and how to protect it from hackers’ actions, a special assessment is conducted - penetration testing (pentest).

What is web application penetration testing

Penetration testing for web applications is a controlled simulation of hacker attacks that helps determine how well a system can withstand real-world threats. The assessment can be carried out both externally and internally within the network to account for different risk scenarios.

During the process, specialists gather information about the environment, identify weak points, and test whether these vulnerabilities can be exploited to breach the system. This approach provides an objective evaluation of the web application’s security level and determines what steps are needed to eliminate vulnerabilities and improve protection.

Online services are continuously accessible from the internet, giving potential attackers many more entry points (such as misconfigured services, vulnerabilities in third-party packages, configuration errors, and weaknesses in authentication). Therefore, web applications require special attention. For businesses, this means that online services must be tested more frequently and more comprehensively.

What a web application penetration test examines

 When and who needs web application pentesting

In many industries, it is a widely accepted standard to conduct penetration testing at least once a year. However, testing should be carried out not only on a regular schedule but also whenever there are significant changes in the company or its infrastructure.

Key reasons to perform a cybersecurity assessment of applications include:

• • Implementation of new technologies, systems, devices, or features in SaaS.
  • Major changes in business processes, expansion plans, or large-scale updates.
  • Discovery of vulnerabilities, introduction of new data, or critical information.
  • New requirements for compliance with security standards and regulations.
  • Increased cyber activity in the industry or attacks on similar systems in other companies.
  • Onboarding of employees, contractors, or partners who may affect security.

It is important to note that hackers today target not only large corporations – startups are also frequently victims of cybercriminals. Therefore, penetration testing of web applications is essential for companies of all sizes.

Penetration testing is relevant across various industries. It benefits financial and healthcare organizations, SaaS platforms and banks, e-commerce businesses, and service providers, not only operators of critical infrastructure but any company that has digital assets and cares about its security and reputation.

The most common web application vulnerabilities

The purpose of penetration testing is to identify vulnerabilities in web applications before real attacks can exploit them.

Here are the 10 most frequent issues discovered by pentesters:

Web application pentesting process

To ensure a thorough and effective security assessment, penetration testing is carried out in accordance with international standards that define clear stages:

1. Information gathering

After agreeing on the details and signing the contract, OSINT is collected from open sources and through interviews with system owners. The network (IP addresses, subnets, devices) is examined using tools such as nslookup, whois, and traceroute. Technologies (web servers, databases, frameworks, versions) are identified, and technical details are collected. All information is recorded in a database for planning and reporting.

2. Reconnaissance

At this stage, passive and active methods are applied. Passive reconnaissance involves gathering data without interacting with the web application: through search engine indexes, social media profiles, public registries, and dumps. Active reconnaissance includes scanning the network and ports (Nmap) to identify live hosts, open ports, and services. DNS analysis, network mapping, and checks of third-party cloud services are also performed.

3. Discovery and scanning

Pentesters examine hosts and services (versions, configurations, open ports). Static analysis of source code and configurations is performed using SonarQube, and dynamic analysis is carried out in the live environment using Burp Suite. Automated scanners such as Nessus and OpenVAS accelerate the detection of known vulnerabilities. The results are supplemented by manual testing to identify uncommon threats.

4. Vulnerability assessment

The next step is processing the identified issues. Vulnerabilities are evaluated based on criteria such as system compromise, risk of data exposure, exploitation complexity, and potential business impact. The obtained assessments are used to prioritize risks, based on which a remediation plan is created and documented in the penetration test report.

5. Exploitation

At this stage, ethical hackers demonstrate the potential consequences of the discovered vulnerabilities, in a controlled environment, they simulate cyberattacks on the web application and, if necessary, show possible data leakage or privilege escalation to assess the real impact. All actions are pre-approved by the system owners, and the results are documented for further security improvements.

6. Final analysis and reporting

The collected information is then analyzed and systematized: data is consolidated, trends are identified, and a detailed report is prepared with an executive summary and supporting evidence. The client is provided with recommendations and a remediation plan to prevent unauthorized intrusions in the future.

7. Implementation and Support

In the final stage, the recommendations are implemented, policies are updated, staff are trained, and, if necessary, a retest is performed after the fixes to ensure that the advice has been correctly applied and all threats have been eliminated.

Penetration test report for a web application

One of the most important stages of testing is preparing the report. This document serves a dual purpose: it provides the client with official confirmation of the work performed and becomes the foundation for further improving security.

What the report includes:

• • System overview. General information about the target infrastructure: architecture, key services, applications, and technologies used.
  • Methodology and tools. Specification of the methods and tools applied during the security assessment.
  • Results and recommendations. A detailed description of prioritized vulnerabilities and ways to remediate them.
  • Evidence. If necessary, the report is supplemented with screenshots, logs, or code snippets that confirm the issues.
  • Conclusions. A summary highlighting the most critical vulnerabilities that require immediate remediation.

A detailed pentest report provides a comprehensive overview of the web application’s security posture and helps maintain compliance with regulatory requirements.

How to maintain web application security

Penetration testing of a web application can be compared to regular medical checkups or vehicle inspections: it is better to detect weaknesses in advance than to face the consequences after an attack.

Moreover, attackers never rest, and with digital progress come new cyber threats. Therefore, it is worth conducting penetration testing periodically to ensure the protection of digital assets and to detect issues in advance.

Here is what our experts recommend for companies that care about the security of their web applications:

1. Integrate web application pentesting into the development process (SDLC)

This is the most cost-effective and straightforward way to address vulnerabilities. During coding, mistakes often occur that can give attackers access to data or systems. Such vulnerabilities are particularly dangerous because they can lead to data breaches. If a project is released without testing, technical debt accumulates – developers have to revisit old code, spend time on fixes and patches. This is more expensive and time-consuming than performing testing in advance.

2. Make penetration testing regular

For small companies and startups, one test per year is sufficient. This helps to detect vulnerabilities in time, reduce the risk of attacks, and meet regulatory requirements. For financial institutions, government agencies, telecom, industry, and e-commerce, it is recommended to conduct tests more frequently, every six months. For SaaS and organizations with complex networks and regular infrastructure changes, quarterly testing is optimal, as new vulnerabilities appear more quickly.

Pentesting: Not a luxury, but an investment in security

Unlike traditional desktop software, web applications provide users with more functionality and convenience, but they can also bring additional costs. Since such services are accessible via the internet, they are constantly exposed to attack attempts. Therefore, Datami experts recommend integrating pen testing into the standard web app development cycle and conducting it periodically after release.

We offer our web application penetration testing service – the best way to reduce risks and strengthen protection, ensure compliance with modern security requirements, and build competitive advantages and trust among clients and partners.