What Is a Website Vulnerability? Understanding Attacks and How to Protect Your Site

How hackers exploit website vulnerabilities

Attackers use a variety of techniques to turn a single flaw into control of a website. Once a website vulnerability is discovered, automated tools and botnets launch attacks within minutes, scanning for weaknesses across CMS platforms and custom applications. These attacks often aim to:

• Access sensitive data such as customer records, login credentials, or financial details.
• Manipulate systems to gain unauthorized control of databases, servers, or core website functions.
• Compromise user trust by injecting spam, redirecting visitors to malicious pages, or stealing active session information.

Even a small misconfiguration can allow cybercriminals to find vulnerabilities in a website and exploit them at scale, which is why regular vulnerability scanning and patching are critical to protecting data and maintaining customer confidence.

Most common vulnerabilities

There are several common website vulnerabilities that are frequently exploited by attackers. While this isn’t an exhaustive list, like the OWASP Top 10, it highlights the weaknesses most frequently found when security teams scan or check a website for vulnerabilities.

SQL injections

SQL injection vulnerabilities occur when untrusted user input is inserted into SQL queries without proper handling. Attackers can craft malicious SQL payloads that the application sends to the database, allowing them to read, modify, or delete data and sometimes execute administrative commands, including:

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

Because it can steal data and bypass logins, SQL injection remains 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 have even been linked to a breach of the U.S. Election Assistance Commission and a popular video game forum for Grand Theft Auto, where exposed user credentials highlighted the need for ongoing updates and prompt remediation.

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. This type of website vulnerability targets visitors rather than the website or server itself. Attackers often inject JavaScript so the script executes in the visitor’s browser. Because browsers cannot tell whether the code is legitimate, the malicious script can trigger actions such as:

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

Some of the largest-scale attacks against WordPress have stemmed 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 happens 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. Once injected, these commands can run with the same privileges as the hosting environment, creating serious security risks.

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. Once successful, the attacker can execute remote scripts, giving them a direct path to serious security risks.

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 such as 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 can escalate into a remote file inclusion attack if the attacker can include log files previously seeded with malicious code 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 highly damaging. CSRF attacks trick site users or administrators into unknowingly performing malicious actions for the attacker. Because the request appears to come from a valid session, the website treats it as legitimate, allowing attackers to exploit existing permissions.

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 attacks are particularly dangerous for eCommerce and banking sites, where attackers can gain access to sensitive financial information. One documented 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, critical security risks 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.

Broken authentication and session management

Broken authentication and session management occur when weaknesses in login or session handling allow attackers to impersonate valid users. Flaws such as weak password requirements, predictable session IDs, or improper logout processes give criminals a chance to steal credentials or hijack active sessions.

Successful attacks can lead to:

• Unauthorized access to user accounts or administrative areas
• Theft of personal or financial information
• Full control of a compromised website

This type of website vulnerability remains a frequent target in vulnerability scanning reports, making strong password policies, session timeouts, and regular patching critical defenses.

Impact of website vulnerabilities

Website vulnerabilities pose a serious threat to organizations of every size, especially eCommerce businesses, where stolen data can immediately affect revenue and customer trust. 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. Recent high-profile breaches across retail, healthcare, and education highlight that website security is now a business necessity rather than an optional safeguard.

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. Late 2024 also saw several large-scale WordPress plugin exploits and a Snowflake-related exposure, showing that high-impact breaches continue to emerge beyond the original MOVEit event.

As recently as July 2025, a critical flaw in the “Alone – Charity Multipurpose” WordPress theme (CVE-2025-5394) allowed unauthenticated attackers to upload arbitrary plugins and achieve remote code execution. Security researchers recorded more than one hundred thousand exploit attempts within days of disclosure, showcasing how quickly attackers act when a new website vulnerability becomes public.

These incidents highlight how a single website vulnerability can ripple across industries, from healthcare to higher education, and why data breaches remain one of the most costly outcomes of a successful attack.

How to find vulnerabilities in a website 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. Knowing how to find vulnerabilities in a website starts with regular vulnerability scanning, which uses automated security tools to probe for weaknesses such as SQL injection, cross-site scripting, or insecure configurations. Once flaws are identified, prompt remediation, whether through patching, configuration updates, or removal of outdated components, reduces the window of opportunity for attackers.

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 security updates and vulnerability patches for their applications, and it is important to perform these updates quickly. 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. A WAF filters incoming requests and blocks malicious traffic before it reaches the application, stopping automated scanners, known spam or attack IP addresses, and suspicious user input. A WAF helps reduce the number of exploits that ever reach the site and lowers the risk of new website vulnerabilities being discovered by inspecting requests in real time.

Sanitize all user input

Input sanitization limits what user-supplied data can contain so it cannot be interpreted as executable code. By filtering and validating every field that accepts user input, such as search boxes, comment forms, and upload areas, this process helps prevent attacks like cross-site scripting and SQL injection. Controlling the characters, formats, and data types accepted by a site makes it far harder for attackers to sneak harmful scripts into normal website functions. Even small gaps in how input is handled can allow malicious code to run inside a visitor’s browser or interact with a database in dangerous ways.

Secure server and application configurations

Secure configuration focuses on tightening the default settings of servers, databases, and applications to reduce exposure. Many breaches stem from simple oversights such as leaving unnecessary services active, using default passwords, or failing to disable test pages. Reviewing system settings, removing unused features, and applying hardened configuration templates lowers the chance that a single misstep will create a new website vulnerability. Because attackers often scan for these predictable weaknesses first, strong configuration practices remain one of the most reliable defenses against opportunistic exploits.

Use a malware and website vulnerability scanner

Your last line of defense is the use of a reputable automated malware scanner. It is recommended that you find one that can automatically identify vulnerabilities and remove known malware. Try our free external website scanner in the meantime 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. Combining automated scans with manual checks provides a more complete view of potential threats and helps uncover issues that automated scanners might miss.

SiteLock: web application and website security you can trust

Understanding the weaknesses hackers target is only the first step. Regular scanning and automated patching are what keep a site secure day after day.. Website vulnerabilities can lead to stolen data, service interruptions, and lasting damage to customer trust, making proactive protection a business necessity.

SiteLock’s website security plans include continuous vulnerability scanning, malware removal, and automated patch deployment to help keep your site safe.. If your site has already been compromised, learn how we help fix hacked websites quickly and securely.