What Is an XSS (Cross-Site Scripting) Attack?

What Is an XSS (Cross-Site Scripting) Attack?

What Is an XSS (Cross-Site Scripting) Attack?

 Protection against top vulnerabilities like Cross-Site Scripting (XSS) is critical because sites store important information. XSS attacks can have a wide range of damage ranging from hackers spreading worms on websites to hackers stealing sensitive data such as identity theft or even committing financial crimes. Then what is an XSS attack?

What Is an XSS Attack?

Cross-Site Scripting or XSS attack is a security exploit in which an attacker places malicious client-end code onto a web page.

This has been the most prevalent attack that has been around for over three decades now. All major websites have been affected by the exploitation of this vulnerability.

Attackers using XSS vulnerabilities steal user data, or control user sessions, run malicious code or even use it as a component of a major phishing scam.

XSS Attack Types

XSS attacks can be broadly classified into the following 3 categories:

1. Reflected XSS

Reflected XSS is also known as non-persistent or persistent XSS attack. In case of reflected XSS attack, the malicious script is bounced to another website in the user's browser. This occurs when user input from a URL or POST data is reflected on the page without being saved, allowing an attacker to inject malicious content.

This means that an attacker must send a malicious URL or post form to the victim to enter the payload, and the victim must click on the link. This kind of payload is also generally caught by the built-in XSS filter in the user's browser, such as Chrome, Internet Explorer or Edge.

2. Stored XSS

Stored XSS, also known as persistent XSS, includes injecting malicious code directly into web applications. This occurs when the payload is stored, for example in a database and then executed when the user opens a page in a web application.


DOM XSS is a form of XSS attack where the malicious script is present in the Document Object Model instead of the HTML. In reflected and stored Cross-Site Scripting attacks, you can see the vulnerability payload in the response page but in DOM-based XSS, the HTML source code and the attack response will be exactly the same i.e. the payload cannot be found in the response. It can only be observed at runtime or by probing the page's DOM.

How XSS Attacks Work

XSS attacks are different from most application layer attacks. Here, the attacker attacks the user application and not the application or server. XSS attacks work by placing malicious code, usually using client-side scripts, into the output of a web application.

Traditionally, most websites have multiple injection points such as search fields, online feedback forms, cookies which appear as soft targets for any cross-site scripting.

One of the most common motives behind XSS attacks is to gain insight from cookie data. Because cookies are usually used in the wrong method to store information like Session ID, user preferences or even login details of a user.

Client-side scripts have no direct impact on server-side information. However, there are still loopholes in the site's security using DOM (Document Object Model) manipulation to modify form values or redirect form actions to submit data submitted on the attacker's website.

XSS Attack Impact

Damage due to XSS vulnerability attacks can be diversified when it occurs in web applications. These range from hijacking user sessions and, when used with social engineering attacks, can result in loss of sensitive user data. With XSS attack exploits, an attacker can impersonate a victim and take over his or her account.

Preventing XSS Attacks

There are several steps and strategies that website owners can use to prevent XSS attacks. Some of them are:

1. Site Security Analysis

To prevent XSS attacks, website owners can even use a website vulnerability scanner such as Sucuri or VirusTotal to analyze site security. It helps website owners to know full audit information about security weaknesses and vulnerabilities present in their site. This also ensures that their website is safe and trustworthy.

2. Add SDL

SDL stands for Security Development Lifecycle. Adding SDL in web applications can limit the number of coding errors and security breaches.

This helps developers build highly secure software, including guarding against XSS attacks. SDL assumes that all data received by the web application is from an unreliable source, even if the data comes from a user who has logged in multiple times.

3. Adopt Crossing Boundaries Policy

The crossing boundaries policy allows authenticated users to re-enter their login information before granting the user access to certain pages and services on the website.

Even if the user is an authenticated person and has a cookie that allows them to log in automatically. Website owners can reset and require users to enter their login credentials on certain web pages.

The crossing boundaries policy can be extended further so that sessions will be terminated automatically if two IP addresses have the same session data.

4. Using the Correct Meta Tags

Using the meta tags given below reduces the number of possible instances of XSS script injection.

<META http-equiv="Content-Type" content="text/html; charset= ISO-8859-1">


So what is an XSS attack? XSS is an attack that has the potential to be one of the most dangerous attacks that occur on websites. This could be a consequence that no owner would possibly live up to. People can prevent XSS attacks on their websites by taking the steps discussed in this article.

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Resa Risyan

Just an ordinary person who wants to share a little knowledge, hopefully the knowledge I provide can be useful for all of us. Keep in mind! Useful knowledge is an investment in the afterlife.

Also, read the article about What Is A Proxy Server And How Does It Work?. And see you in another article. Bye
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