What Is a Cross-Site Scripting Attack and How to Prevent It?


Cybersecurity has become crucial as the number of attacks on businesses across every industry is increasing daily. For everyone to keep up with the trends, the security infrastructure should be top-tier. Even a minimal vulnerability can be critical to business and lead to data loss and downtime.

Many websites and businesses fall victim to malicious attackers because they downplay the significance of cybersecurity. Cross-site scripting attacks are among the most dangerous cyberattacks and can seriously harm any website.

What is a cross-site scripting attack?

Cross-site scripting or XSS attack is a cyberattack that works when the browser of the victim system is manipulated. It is done by executing malicious JavaScript in the user system. As a client-side injection attack, XSS is performed using malicious JavaScript in legitimate web applications or browsers.

Vulnerabilities come from online forums, messages, and web pages that allow comments and interactions. The malicious code fools the browser and executes malware when the website is loaded. It can lead to losing control of the data and functionality of the website or application. XSS attacks are possible in many languages like CSS, VBScript, ActiveX, and Flash. Moreover, the most attacked language is JavaScript, as most browsers use JavaScript.

What do attackers do with JavaScript?

The malicious script is injected into the web browser of the user. With this, vulnerable websites carry the code whenever the user interacts with them. Attackers use this for stealing sensitive data and session hijacking.

Attackers can inject code to execute clickjacking attacks, malware distribution attacks, crypto-jacking, etc.

What is cross-site scripting?

It is a weakness in a web application that allows attackers to insert nefarious code into a website. This attack occurs when an attacker can inject their code into a page that other users view. The injected code can then execute in the context of the victim's browser, allowing the attacker to steal sensitive information or perform unauthorised actions.

Types of cross-site scripting attacks:

Cross-site scripting attacks are of many types. Here are some of the most severe XSS attacks:

Stored XSS

It occurs when an attacker can insert malicious code on a website in places like comments or messages. When other users view the page, the code is executed in their browser, causing harm.

Reflected XSS

Another type is reflected XSS, where the malicious code is shown to the user in an error message or search result. The attacker can steal sensitive information or gain unauthorised access when the browser executes the code.

DOM-based XSS

This is also a major XSS. This activity involves modifying a web page's Document Object Model (DOM) on the client side without modifying the HTML code. It makes it difficult for users to detect this type of cross-site scripting.

Reverse XSS

Reverse XSS is possible if a hazardous code like XSS harms your company. Another kind of attack involves the introduction of harmful code into a web page. A server-side script afterwards runs the code. This may result in the theft of private information from the server. It may also result in a variety of other malicious actions.

Blind XSS

If your team is untrained, blind XSS may happen in your company. Although the attacker cannot see the attack's results immediately, it might influence your web app. It differs a little bit from other attacks. They depend on the victim's behaviour to recover and reveal the stolen data. Because this attack doesn't cause any noticeable modifications to the website, it might be challenging to identify and fight against.


It can affect your business negatively when the attacker tricks the victim into executing malicious code by masking it as a harmless script. Users get tricked when they need to follow the proper strategy for this. When the victim copies and paste it into their web browser's console, it affects the whole website. This attack often uses social engineering tactics to access a victim's social media or email accounts.

XSS attack examples

XSS attacks have been around for a while now. With harmful capabilities, they can affect any website that has vulnerabilities in the code. It can also affect your business like it has affected some popular names. Here are some examples of cross-site scripting attacks that have occurred in the past:

  • Yahoo Mail was attacked by an XSS cyberattack in 2012 by a group of a hacker group named D33Ds. Hackers stole the user's email details and spread the attack to user contacts with the help of creating malicious mail.
  • Twitter faced an XSS vulnerability in 2014 on the Tweetdeck client side, where attackers could follow users, post tweets, and send messages.
  • In 2014, eBay was hit by an XSS attack that allowed attackers to steal users' login credentials and personal information. The attack was carried out using a spoofed eBay login page sent to users via email.
  • One of the most popular gaming platforms, Fortnite, faced XSS vulnerabilities in 2019. It was on a retired page that allowed attacks to access unauthorised data. A fake login page created with this would severely affect user data.

How can an XSS vulnerability affect a website?

It can affect any website. Here are three types of web apps that can be affected by XSS vulnerabilities:

Static content

If we talk about the impact of XSS in web apps, there is minimal impact on websites with static content. Users do not need to log in; it can help them stay anonymous. All the details of the website are publicly available, and no user data is there that can be attacked.

Sensitive data

If you are considering sensitive user data, then cross-site scripting can be harmful. Many industries take sensitive user data, like healthcare and financial organisations. These attacks can gain access to user accounts and steal sensitive data. Moreover, it can lead to financial loss, identity theft, or other serious consequences.

Privileged users

Suppose an attacker can use XSS to take over the session of a privileged user, such as the web application administrator. In that case, they can gain complete control over the application and compromise all its data. This can +have serious consequences, especially if the compromised user has access to sensitive information or critical system resources.

Cross-site scripting attack vectors

Many XSS attack vectors can be used to steal information and compromise the security of web apps. Here are some of the vectors used in XSS attacks:

  • A script tag that can be used to reference external JavaScript.
  • JavaScript events that can be applied in tags like on-error and on-load.
  • Event attributes are provided with the body tag.
  • Vectors that allow XSS to embed HTML into dynamic pages.
  • Vectors that can be used to execute JS code.
  • Vectors where background attributes to any image.
  • Tags can be used as background references like a script.
  • Vectors that allow external site scripts.

Cross-site scripting vs SQL injection

More and more businesses are choosing web applications, which have become one of the most used trends in the technological world. Cyberattacks are also increasing in web apps, and cross-site scripting and SQL injections are two of the most deadly attacks.

Here are some of the differences between cross-site scripting and SQL injection attacks:

Cross-site scripting (XSS) SQL injection
It targets web browsers and can modify the content of web pages. It targets databases and can modify, add, or delete data in databases.
These attacks can be detected using automated web application scanners. These attacks can be detected using vulnerability scanners or manual testing.
It injects malicious scripts into web pages and can steal sensitive user data. It injects malicious SQL into database queries and manipulates databases.
Exploits vulnerabilities in client-side code. Exploits vulnerabilities in server-side code.
It can lead to defacement of web pages. It can lead to data loss or corruption.
These attacks rely on social engineering to trick users into executing scripts. These attacks rely on input validation vulnerabilities in the web application.
Attackers use it to steal cookies and launch session-hijacking attacks. Attackers use it to bypass authentication or authorisation checks.
These attacks are difficult to detect and exploit in modern web applications.. It is easy to detect and exploit in poorly designed or legacy applications.
It affects all users who visit a vulnerable web page. It affects specific users or groups of users.
These attacks can be prevented by input validation and output encoding. These types of attacks can be prevented using prepared statements and stored procedures.

How to prevent cross-site scripting?

Cross-site scripting (XSS) can lead to the theft of sensitive information, such as login credentials, or even full control of the session. To prevent XSS attacks on your website, you must take certain steps to ensure user input is properly validated.

Here are some of the best methods for cross-site scripting prevention:

Input value validation

The best practice is to test the input format, length, and type. Removal of threatful tags and characters from HTML can help as well.

Using web app firewall

For cross-site scripting prevention, a quality WAF can be installed. With this, you can manage the DDoS attack and prevent malicious requests from reaching the user's website.

Escape User Input

It can be done by eliminating all user input before displaying it on your website. This prevents the browser from interpreting the input as HTML or JavaScript code and instead displays it as plain text.

Setting a policy

Web apps can set a strict policy on content and define the content types to prevent any mishappening. Websites need to add a header to the HTTP response for this. It can be used to prevent additional extra input.

Limit Cookies and Session IDs

Information like login credentials and authentication details are stored temporarily on web apps. XSS attacks can be prevented by limiting stored cookies and session IDs. Data encryption and validation is also a good strategy for this.

How to fix cross-site scripting?

Immediate action should be taken if a company faces a cross-site scripting attack. Here are some steps that a business can take to fix and limit XSS attacks:

Identifying the attack type

A web app needs to discover the type of XSS attack before anything else. It can be done through constant network monitoring. With security scans on the app infrastructure and network, unusual activity can be spotted for making different decisions.

Limit harm

Identify the attack's type, then contain it to limit further harm. Affected systems can be disconnected from the network, or affected user accounts can be disabled. The affected system must also be temporarily shut down so it can not spread further.

Assess the threat

Web apps need to know what damage has been done to the web app. Practices like reviewing system logs and backups can be done to determine what data has been compromised.

Notify relevant parties

Web app owners can notify customers and regulatory agencies about the attack and data stolen. This can help to mitigate the damage caused by the attack and maintain trust with users.

Implement fixes and patches

It is important to implement fixes and patches to prevent the attack. This can include updating software, implementing access controls, and conducting employee security training.

Monitor and review the system

For your system or any business platform, monitoring the system is a great way to ensure we are going in the right direction with XSS. Reviewing security measures for preventing potential XSS future attacks is a vital step. It can be done by implementing security scans and staying up-to-date on the latest security threats and trends.

Stay cyber resilient with web apps

Many businesses are using web apps and delivering a good user experience. These apps are used for online shopping, communicating with others, and many more reasons. Almost every big brand uses these to reach more users and provide a quality user experience. Cybersecurity is a growing concern, as online attacks can harm a business. You need the best security posture to stay cyber resilient with the increasing number of attacks. With our web app development service, we ensure you get the best security for user data.

Enquiry Now
This website uses cookies to ensure you get the best experience on our website. Accept