What Is a Website Vulnerability and How Can Hackers Exploit Them?

Websites experience multiple attacks per day. A website vulnerability is a weakness or misconfiguration in a website or web application code that allows an attacker to gain some level of control of the site and possibly the hosting server. Most vulnerabilities are exploited through automated means, such as botnets. Cybercriminals create specialized tools that scour the internet for certain platforms, like WordPress or Joomla, looking for common and publicized vulnerabilities. Once found, these vulnerabilities are then exploited to steal data, distribute malicious content, or inject defacement and spam content into the vulnerable site.

Most common vulnerabilities

There are six common types of website vulnerabilities that are frequently exploited by attackers. While this isn’t an exhaustive list, like the OWASP Top 10, of all the possible vulnerabilities a determined attacker may find in an application, it does include some of the most known vulnerabilities websites contain today.

SQL injections

SQL injection vulnerabilities refer to areas in website code where direct user input is passed to a database. Bad actors utilize these forms to inject malicious code, sometimes called payloads, into a website’s database. This allows the cybercriminal to access the website in a variety of ways, including:

• Injecting malicious/spam posts into a site
• Stealing customer information
• Bypassing authentication to gain full control of the website

Due to its versatility, SQL injection is one of the most commonly exploited website vulnerabilities. It is frequently used to gain access to open source content management system (CMS) applications, such as Joomla!, WordPress, and Drupal. SQL injection attacks, for example, have even been linked to a breach of the U.S. Election Assistance Commission and a popular video game forum for Grand Theft Auto, resulting in exposed user credentials.

Cross-site scripting (XSS)

Cross-site scripting occurs when attackers inject scripts through unsanitized user input or other fields on a website to execute code on the site. Cross-site scripting is used to target website visitors rather than the website or server itself. This often means attackers are injecting JavaScript into the website so that the script is executed in the visitor’s browser. Browsers are unable to discern whether or not the script is intended to be part of the website, resulting in malicious actions, including:

• Session hijacking
• Spam content being distributed to unsuspecting visitors
• Stealing session data

Some of the largest-scale attacks against WordPress have been from cross-site scripting vulnerabilities. However, XSS is not limited only to open source applications. For example, a cross-site scripting vulnerability was found in gaming giant Steam’s system that potentially exposed login credentials to attackers.

Command injections

Command injection vulnerabilities allow attackers to remotely pass and execute code on the website’s hosting server. This is done when user input that is passed to the server, such as header information, is not properly validated, allowing attackers to include shell commands with the user information. Command injection attacks are particularly critical because they can allow bad actors to initiate the following:

• Hijack an entire site
• Hijack an entire hosting server
• Utilize the hijacked server for botnet attacks

One of the most dangerous and widespread command injection vulnerabilities was the Shellshock vulnerability, which impacted most Linux distributions.

File inclusion (LFI/RFI)

Remote file inclusion (RFI) attacks use include functions in server-side web application languages like PHP to execute code from a remotely stored file. Attackers host malicious files and then take advantage of improperly sanitized user input to inject or modify an included function into the victim site’s PHP code. This inclusion can then be used to initiate the following:

• Deliver malicious payloads that can be used to include attack and phishing pages in visitors’ browsers
• Include malicious shell files on publicly available websites
• Take control of a website admin panel or host server

Local File Inclusion (LFI), like remote file inclusion, can occur when user input is able to modify the full or absolute path to included files. Attackers can then use this vector to gain, read, or write access to sensitive local files—for example, configuration files containing database credentials. The attacker could also perform a directory traversal attack, amending an included file path to review the backend and host server files and expose sensitive data. A local file inclusion attack has the potential to become a remote file inclusion attack if, for instance, the attacker can include log files that were previously seeded with malicious code by the attacker through public interaction.

These types of vulnerabilities are frequently used to launch other attacks, such as DDoS and cross-site scripting attacks. They have also been used to expose and steal sensitive financial information, such as when Starbucks fell victim to an inclusion attack that compromised customer credit card data.

Cross-site request forgery (CSRF)

Cross-site request forgery attacks are less common but can be quite damaging. CSRF attacks trick site users or administrators into unknowingly performing malicious actions for the attacker. As a result, attackers may be able to take the following actions using valid user input:

• Change order values and product prices
• Transfer funds from one account to another
• Change user passwords to hijack accounts

These types of attacks are particularly vexing for eCommerce and banking sites where attackers can gain access to sensitive financial information. A CSRF attack was previously used to seize all control of a Brazilian bank’s DNS settings for over five hours.

Security misconfigurations

When security controls and configurations in any layer of a website, such as application, web server, network services, platform, framework, and databases, are set up incorrectly, security issues can occur, including:

• Using legacy components (unused pages, features, unpatched software, etc.)
• Leaving unnecessary admin ports open
• Enabling outbound connections to internet services, directory services, and so on

Commonly known security misconfigurations encompass broken authentication, broken access control, misconfigured cloud storage permissions, inadequate encryption settings, and failure to disable unnecessary services or features.

Impact of website vulnerabilities

Website vulnerabilities pose a significant threat to eCommerce businesses, impacting both their reputation and bottom line. When exploited, these vulnerabilities can lead to unauthorized access to sensitive data. ​Therefore, it compromises the integrity of the entire website. Personal data obtained through a user's browser can also be exploited to execute malicious scripts, further exacerbating the cybersecurity threat. Website security is not a luxury but a necessity.

Increase in data breaches

In 2023, the global landscape faced a surge in cyber attacks and data breaches, with statistics revealing a staggering 694 reported breaches and over 612.4 million breached records worldwide. Among the notable incidents, the MOVEit breach in May 2023 impacted an estimated 17.5 million individuals, exploiting vulnerabilities in Progress MOVEit software. Affected organizations included prestigious institutions like Johns Hopkins University and the University of Utah.

These breaches underscore the critical need for robust security measures, especially in educational and healthcare sectors, which remain prime targets for cybercriminals.

How to find vulnerabilities and fix them

There are easy steps you can take to manage and prevent vulnerabilities from allowing hackers to gain unauthorized access to your website and sensitive information.

Update all applications

The first critical step in securing your website is to ensure all applications and their associated plugins are up-to-date. Vendors frequently release imperative security patches for their applications, and it is important to perform these updates in a timely manner. Malicious actors stay in the loop on open source application news and are known to use update notices as a blueprint for finding security vulnerabilities. Subscribing to automatic application updates and email notifications on critical patches will help you stay one step ahead of the attackers.

Use a Web Application Firewall (WAF)

Web application firewalls are the first line of defense against those probing your website for vulnerabilities. WAFs filter out bad traffic from ever accessing your website. This includes blocking bots, known spam or attack IP addresses, automated scanners, and attack-based user input.

Use a malware and website vulnerability scanner

Your last line of defense is the use of a reputable automated malware scanner. It is recommended you find one that can automatically identify vulnerabilities and remove known malware. Try our free external website scanner to look for malicious code on your site, ensuring it is up-to-date and secure.

More advanced programmers may opt to manually review their code and implement PHP filters to sanitize user input. This includes methodologies such as limiting image upload forms to only .jpg or .gif files and whitelisting form submissions to only allow expected input. However, automated and manual security checks provide a more holistic approach to cybersecurity.

Web application security is paramount

Understanding the types of vulnerabilities that hackers may attempt to use to exploit your web applications is an important first step to securing your website. Vulnerabilities can have dire consequences for not only your website and server but for your customers’ data as well.

See how SiteLock's website security plans can keep your websites safe and patch vulnerabilities. If your site has already been compromised, learn how we help fix hacked websites.