What Is Cross-Site Scripting (XSS) Attacks

Cross-site scripting (XSS) vulnerabilities remain a major threat to web applications as attackers can exploit XSS attacks to gain control of an account and steal personal information like passwords, bank account numbers, credit card information, personally identifiable information (PII), social security numbers and more. In this article, we will explain what cross-site scripting is, describe the different types of XSS vulnerabilities and explain how to find and prevent them. Also known as XSS, it is one of the most common vulnerabilities in web applications and can cause serious damage if it is not mitigated in time.

The variety of XSS-based attacks is unlimited and can include private data, cookies and other session information to attackers, redirecting the victim to content that has gotten out of control or performing other malicious operations on Users under the disguise of a vulnerable website. Worse, victims of XSS attacks are often users and developers of web applications who are not even aware that they are being attacked. Although these attacks are widespread, they are a low priority for the cybersecurity community because their impact is limited.

In many cases, XSS can be executed in a more direct way, e.g. By e-mail. In many cases, reflective XSS attacks rely on phishing emails that shorten or obscure the URL sent to the target user. When an XSS attack has no specific target, the attacker exploits a vulnerability in the application or website to exploit those unlucky enough to be victims.

In such cases, the injected malicious script migrates to a vulnerable website and reflects the attack on the victim’s browser. The attacker inserts a malicious string via the web page the victim is visiting, which is treated as source code by the victim browser. When the victim accesses the specially created link, the script is executed in the victim’s browser.

In a remote code execution (RCE) attack, malicious JavaScript is executed in the user’s browser. The web server serves the victim as the browser of a page with the attacker’s payload as part of the HTML body. The attacker injects the payload into the web page database or submits a vulnerable form containing the malicious JavaScript content.

XSS attacks allow attackers to inject client scripts into web pages that are viewed by other users. Client-side code injection attacks (XSS) allow the attacker to execute malicious actions within the victim’s web browser. Tools in the arsenal of cross-site scripting attacks include the theft of cookies that use information stored in a user’s web browser cache to identify a user in a specific connection session.

A classic method of transmitting session and cookie data is for an attacker to send an HTTP request from an attacker-controlled server to the user’s web browser. If the web application does not process the data in this way, the attacker can launch a script-based attack on other users.

An injectable script presents itself as a false message, a search result or a similar action or as a malicious link. These attacks, also known as persistent XSS, occur when a web application shares in subsequent HTTP responses data from an untrusted or unverified source.

With the user rights of the victims and access to the application, the attacker is able to gain full control over the functionality and data of the applications. Another variant of the XSS approach is the Cross-Site Request Forgery attack, which forces the end-user to perform unwanted actions. An attacker can trick a user of a web application into changing an e-mail address or transferring money.

Websites and web applications are vulnerable to XSS because they do not use sanitized user input and output that they generate. An attacker could exploit an XSS vulnerability in a web page to execute arbitrary JavaScript in the browser of the user and compromise the security of the web page and its users.

In short, an XSS vulnerability occurs when input entering a web application is not validated and the output in the browser does not escape display. Web apps are vulnerable to XSS attacks when the user provides input that can be executed as code.

As you can see, the main difference between reflected and persistent XSS attacks is that the latter consider the user of the vulnerable website or app to be the target of the attack. Another type of XSS attack is a DOM-based vulnerability in the client-side scripts that the website/app provides to the visitor. An example of a DOM-based XSS vulnerability is a bug in a number of jQuery plugins in 2011.

A cross-site scripting attack occurs when an untrustworthy source is allowed to inject its own code into a web application and this code contains dynamic content that is delivered to the victim’s browser. The malicious script is delivered in form of JavaScript code from the victim browser but the exploit can also contain malicious executable code from many other languages such as Java, AJAX, Flash and HTML. This is one of the most common vulnerabilities in web-based applications, and because their servers are connected to systems they rely on, attackers can include malicious content in the contents of a compromised website.

When the resulting combination of content arrives on the web browser client-side, it is supplied by a trusted source that works with permissions granted by the compromised website.

By finding a way to inject malicious scripts into a web page, an attacker can gain extended access to sensitive page content, session cookies and a variety of other information the browser manages on behalf of the user. Advantech WebAccess Version 8.1 allows remote injection of arbitrary web scripts and HTML to authenticated users. Vulnerabilities in Wonderware and Information Servers allow attackers to inject arbitrary code into web pages viewed by other users bypassing client-side browser security.

Cross-site scripting (XSS) attacks are a type of injection that injects malicious scripts into benign or trusted sites. They occur when attackers use a web application to send malware in the form of browser-side scripts to various end-users. The bugs that allow XSS attacks to succeed are widespread and occur when web applications use user input and output from web applications to generate, validate, or encrypt user input.

Cross-Site Scripting (XSS) is a common attack vector that injects malicious code into a vulnerable web application. A successful cross-site scripting attack can have devastating consequences for the reputation of an online company and its relationship with its customers. XSS differs from other web attack vectors such as SQL injection in that it does not target directly the web application itself.


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