What’s an XSS Vulnerability?

If you’ve ever visited a website and noticed an XSS vulnerability, you’ve probably wondered what the attacker’s purpose is. They may want to gather user data, masquerade as the user, or redirect the user to a malicious website. Here’s an example of an XSS attack. You can’t see it, but it works! The attacker simply uses the XSS vulnerability to gain access to sensitive information or redirect a user to an inappropriate website.

Stored and Reflected XSS Attacks

Stored and Reflected XSS attacks are both methods of injecting malicious code into a web application. A stored XSS attack is when the attacker intercepts a legitimate request and adds malicious code to the server. The impact of this attack is greater than a reflected XSS attack, because each user visiting the compromised website will be exposed to the malicious code. This method is especially dangerous when a website allows user sharing.

In one of the most common reflected XSS attacks, the perpetrator inserts malicious Javascript code into an ecommerce website. When customers click on a compromised listing, they are redirected to a login page where the attacker can access sensitive personal information and credit card data. This attack is also referred to as a’replay’ attack. The perpetrator can also steal passwords or account credentials from the vulnerable website.

Types of XSS Vulnerabilities

XSS vulnerabilities are web application security flaws that can allow an attacker to inject malicious content into a web page. These vulnerabilities are typically caused by poorly implemented HTML escape sequences that allow an attacker to insert malicious JavaScript code into a web page’s text. This code can then be executed within the server context. Fortunately, most browsers are equipped with built-in anti-XSS filters that help protect users from reflected and persistent XSS.

JavaScript XSS vulnerabilities are one of the most common types of XSS vulnerabilities. This type of XSS vulnerability occurs when an attacker injects malicious code into the affected application and leaves it permanently stored on the target server. These malicious scripts then display on normal pages returned during browsing. Stored XSS is especially important because the attacker doesn’t need to target a specific victim or lure them to a third-party website. These flaws can compromise any information received by the vulnerable web application.

How to Protect Yourself

XSS, or cross-site scripting vulnerabilities, are attacks that exploit browser weaknesses. They happen when an application uses data from an untrusted source and includes it in an unsafe way. The data could come from an HTTP request, social media post, or network monitoring application. Fortunately, there are many ways to protect yourself from reflected XSS attacks. Encryption, validation, and escaping/encoding techniques can protect your website from this type of attack.

The most important defense against an  Vue XSS attack  is to encrypt user-controllable data. In most cases, this means applying a form of validation before the value is written. However, the type of validation required differs depending on the context. For example, a value in a JavaScript string requires different escaping from that used in HTML context. Encrypting user input is not enough. Validating the values before writing them to a file is also a key defense against XSS attacks.

Alternate XSS Syntax

The Alternate XSS Syntax vulnerability affects websites and web applications that store user input. This can be in the form of user-supplied data in a message forum, visitor log, comment field, and other places. The data is then retrieved by the victim through a web application’s request and rendered in the browser. The attacker’s payload may be stored in the browser or HTML5 database and never sent to the target server.

An attacker can take advantage of this flaw to inject malicious content into web application output. In the case of a login form, attackers can insert malicious JavaScript to steal cookies or execute actions with the permission of the user. XSS vulnerabilities fall into two categories: reflected and persistent. The former involves the injected content appearing in output directly after the request. These types of XSS vulnerabilities don’t require user interaction, while the latter involves storing the user input and incorporating it into later outputs.