Six Most Common Vulnerabilities Found During Penetration Testing
Best practices
6 mins read
January 2, 2024

6 most common vulnerabilities found during penetration testing

According to a new report by Juniper Research, over 33 billion records are stolen as a result of cyberattacks. Because of the increasing cyberattacks, penetration testing is no longer an option but a necessity – especially for any business handling data, gathering financial details, or establishing personal intellectual property.

Tania Zhydkova
Denis Matusovskiy

In this post, we will briefly cover penetration testing, along with discussing the six most common vulnerabilities that are found during this test.

Penetration testing, or pen testing, is the replication of the actions taken by malicious hackers but in an ethical way. It is a systematic process used to evaluate the security of an infrastructure to exploit vulnerabilities, which may be present in operating systems, software, and hardware flaws, inadequate configurations, or employees’ susceptibility to phishing and social engineering attacks. In addition, such assessments are used to validate the effectiveness of defensive systems and users’ adherence to security policies. Essentially, organisations can prevent or limit the damage that attackers could cause if they successfully exploit security vulnerabilities.

To identify any weak points in a system’s defences that an attacker could take advantage of, different types of tests are performed, each with varying goals, scope, and requirements. These include, but are not limited to, network penetration testing (external, internal, and perimeter devices), web application pen testing, cloud penetration testing, database penetration testing, and mobile device penetration testing. Pen testers also conduct tests for various consumer-grade products like VPNs, for example, to identify any weaknesses and provide the companies with the information required to fix such issues and secure their product.

Pen testers look for ways of exploiting known vulnerabilities, in addition to using their skills to find out any specific weaknesses, or unknown vulnerabilities, in a company’s security arrangements. Here are the six most commonly reported vulnerabilities discovered during  penetration testing:

Use of default credentials

Many a time, manufacturers set default credentials to enable first-time configuration. Penetration testers often find that the network devices and systems have been improperly configured and default login credentials are still in place. Attackers are aware that devices and networks are usually left with default credentials, and with some guesswork, they can quickly enter those systems to find and steal confidential information. What’s worse, they can even set their own credentials, locking actual administrators and users out in order to continue their plan.

SQL injection

At times, SQL injection vulnerabilities can be easy to find in a web application because of the use of automated pentest tools. This injection works by manipulating any flaw in software where user input is required to access database information. Simply by injecting malicious characters, attackers could alter the workflow of the SQL statement, causing a remote code execution to steal user data and/or otherwise harm the targeted company. It causes significant damage to the business; for instance, the TalkTalk data breach in 2015 by a SQL injection resulted in a £400,000 fine, as well as an adverse effect on the company’s brand image.

Cross-Site scripting (XSS) attacks

Less known than SQL injection, cross-site scripting (XSS) is also among the common vulnerabilities found in web applications. The general use of XSS is to steal user sessions on malicious sites. It is done either by injecting code into a site or creating a malicious URL, which will intercept the session if an unsuspicious user opens the link. This attack can get dangerous when a user’s session has been taken via cross-site scripting. As a result, the attacker leverages user impersonation to access sensitive information, such as bank account details.

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Server security misconfiguration

Server security misconfigurations in software cover a wide variety of vulnerabilities that attackers can exploit. The effect could range from limited information disclosure or significant damage to the impacted system. Many of these issues include deficient application security controls, verbose error messages, default accounts, and so on.

Inadequate access privileges

Every extra user having access to enter and/or access sensitive security systems increased the vulnerability of these systems. Privileges should be allocated only to the people needing them as per the nature of their roles and responsibilities. Remember, it takes hackers to compromise only one such user computer to get a foothold in the network and navigate around servers in order to access more data and confidential information.


Phishing is another form of exploitation that is becoming more widespread with every passing year. According to ESET’s 2021 research, there has been an increase of 7.3% in email-based attacks in just 4 months of 2021, many of which were a part of phishing campaigns. Phishing emails have become far more effective since attackers understand that there are higher chances of clicking on links if the email comes from a sender the recipient knows or, even better, trusts. As a result, the user clicks an  infected link or enters credentials on a fake website. The attacker then gets a foothold on the network and escalates the privileges.

Key takeaways

Application and infrastructure vulnerabilities are a major focus of penetration testing and vulnerability reports executed during the security management life cycle. The vulnerabilities listed above illustrate only the key ways in which hackers can get access to the network, gain administrative privileges, and use them to do unimaginable damage to the business. With pen testing, organisations can establish weaknesses in their network, patch them or source a cybersecurity consultancy to do that, thereby improving overall security.

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