What can be a goal of XSS attack?

If you want to know the goal of an XSS attack, first you need to know  what is an XSS attack, how does it work, and then realize its features as well as its dangers, finally you would figure out the goal of such an attack. You will also become familiar with its different types and the common destructions it could make for you. You probably are curious about the history of this attack, too, and where does this abbreviation come from; if you are, follow this article till the last paragraph.

What is a Cross-Site Scripting attack?

One of the cyber threats to websites or applications is rush. This stands for Cross-Site Scripting. Cross-Scripting Attack is a common type of code injection that rushes targets are web applications, and it does destruct them by detecting their vulnerabilities and injecting malicious code. In this attack, web applications are not directly affected, and instead, users who interact with such sites or applications are potential targets. Its attacks occur when a hacker uses a browser-side scripting style to send malicious code to a victim through  a web application. Attackers take advantage of vulnerabilities in web applications that could cause a successful attack.

An example of Cross-Site Scripting rush

Imagine someone sitting at a computer. The screen shows a File manager, Text editor, Spreadsheet, and the Music player is in the right corner. So far, everything is normal and familiar. But what is not seen in this image is an Internet browser with lots of tabs opened simultaneously. These tabs are full of fun titles, funny movies, sporting goods ads, online stores, and a pay-per-click site for a quick ticket. These sites have one thing in common: they would be difficult to get opened without JavaScript. Then a simple click on the banner ad activates another page. This page contains a script that connects to an online banking site and seamlessly transfers money to the attacker's card from the user account. Fortunately, browsers today eliminate this possibility thanks to the SOP (  Same-Origin Policy  ). SOP ensures that scripts executed on a web page do not have access to erroneous data.

What is Javascript, and how is it related to Cross-Site Scripting savage?

JavaScript is high-level scripting or programming language that allows you to implement web pages with more complexity. This language enables you to have pages with dynamic content. On the other hand, more control over multimedia (text, audio, photos, animation, and video) and many other features make this language more special than other similar languages. Now the question is  why an attacker should try to inject JavaScript code. The consequences of running JavaScript code may not initially be considered a threat. Because most browsers usually run JavaScript in very restricted environments, JavaScript will not have access to the operating system and user files. However, injecting JavaScript code can still be dangerous, and this is possible due to some JavaScript capabilities. As a result, these capabilities can have many benefits for the intruder. Some of them are:

- Obtaining authentication information

- Obtaining private user information

- Sending fake requests due to user access level

-  Create forms and styles on a user-trusted website  to deceive a user

What is the goal of Cross-Site Scripting strafe?

The purpose of the Cross-Site attack is to inject malicious code to run on web pages that trust their users (if we are to be optimistic). These codes will be executed like the codes that reach the Server to the Client and can access all the information that the user can access, such as cookies, Session, etc. In these attacks carried out by hackers, the main purpose is to steal the information of users' information on the site and by injecting JavaScript code into the website, which is very similar to the Brute Force attack. Users' information can include their username, password, email, and bank account information. This code can steal important information from the user's system. When users log in to their user accounts such as email, bank account, and other accounts, their account information, which is the same as cookies, is stored on the user's personal computer, and hackers also steal cookies from the user's system. They use it to access important information.

Cross-Site Scripting types

This vulnerability was initially divided into two types, Stored and Reflected (continuous and non-continuous). But in 2005, Mr.  Amit Klein  defined the third type of XSS, DOM-based. In this section, the purpose is to introduce the types of this, so we will mention the names of these three types, and in the continuation of the article, we will define these three types in detail.

- Server XSS

Server Cross-Site Scripting occurs when an invalid user succeeds in forcing a website to generate data in an HTTP response. The source of this data can be stored from a request or location. Therefore, this Server can be divided into two types: Stored Server and Reflected Server. In this type of attack, malicious code is provided by the Server, and the browser simply executes the code, which means that any script is valid from the browser.

- Client XSS

Client Cross-Site Scripting Occurs when invalid user data attempts to update the DOM with an insecure JavaScript call. A JavaScript call is considered insecure when it can provide a valid JavaScript code to the DOM. Receiving malicious code can be from the browser DOM, or it can be sent from the Server (by an AJAX call or page load). The data source can also be from a request or a location stored on the Client or Server system. So you can have a Reflected Client attack and  Stored Client XSS. Also, since DOM Based attack only runs on the client-side, there is no change in its definition, and this vulnerability is simply a subset of the Client. By these definitions, it's being Reflected or Stored only affects the likelihood of an attack occurring and does not change the nature of the attack.

Protection against Cross-Site Scripting strafe

Applications can be challenging in terms of the complexity of cross-scripting. Therefore, it is difficult to secure them against cross-scripting attacks. But with proper precautions,  you can protect your web application from these attacks.

- You must filter the input received from the user

- In the output, encode the output data to implement a combination of HTML, URL, JavaScript, and CSS encoding to disable it.

- With Web Vulnerability Scanner tools, you can scan your web application for potential Cross-Site Scripting vulnerabilities.

Implement a proper header, block this in HTTP responses that are not expected to include HTML or JavaScript, and make sure browsers execute the desired response.

- You can also implement a  Content Security Policy  (CSP) to curb the harmful effects of any other strafe vulnerabilities.

How to prevent or reduce the risk of these bugs or vulnerabilities

How to completely prevent XSS requires a lot of research on  the performance of the website and depending on the design  of the program, which is not the purpose of this article. Here are some ways to prevent and secure websites in general, and if you pay attention to these, the application will be largely safe against XSS vulnerabilities.

- Lack of support for HTTP TRACE

An attacker would steal cookie data through JavaScript, even if the Client was disabled or did not support the cookie. This type of attack occurs when a user posts a malicious script on a site such as a forum, and a victim user clicks on it.

- Input validation

Validation of inputs is terms and conditions that a programmer must set according to the needs of an input. An example would be not sending letters in fields that only need numbers.

- Escape from suspicious characters

It means censoring some of the characters suspected of attacking.

- Sanitize inputs when rendering them

Doing sanitize while storing information can be problematic because the intruder can usually find a way to store information that Sanitize does not do.

Last word

You now know what is XSS attack and its goals. You may have realized that it is considered a dangerous attack that may cause some problems for you. So pay attention to protection ways mentioned above, to prevent your information from getting stolen.