Mastering Payload Xss Prevention: A Developer’s Handbook – This blog will help developers understand XSS, its types, and how to recognize and prevent it. XSS stands for cross-site scripting, which is a type of loophole.
Remember when a vulnerability was discovered in Microsoft Exchange Server that allowed cross-site scripting (XSS) attacks? This RXSS can lead to unauthorized access to email accounts, phishing attacks, and other actions that can change the state of the affected application. XSS attacks pose a major threat because they allow attackers to execute malicious code in a user’s browser, which can lead to the theft of sensitive data or accounts. However, Microsoft fixed the problem by releasing a patch to fix the vulnerability. This highlights the importance of updating software and regularly assessing security risks.
Table of Contents
- Mastering Payload Xss Prevention: A Developer’s Handbook
- Tutorial On Cross Site Scripting (xss) Prevention In
- Cross Site Scripting Prevention】protect And Prevent Xss
- Mastering The Art Of Red Teaming: Advanced Techniques And Strategies For Penetration Testers
- What Is Cross Site Scripting (xss) ?
- Xss Attacks: Best Prevention
- Xss In Practice: How To Exploit Xss In Web Applications (walktrought Into Google Xss Game) — Stackzero
- Common Questions About Saas Product Development
Mastering Payload Xss Prevention: A Developer’s Handbook
XSS stands for cross-site scripting, a type of security vulnerability that allows attackers to inject malicious scripts into a web page viewed by other users.
Tutorial On Cross Site Scripting (xss) Prevention In
What happens if a web application has XSS? When a user accesses an application with a cross-site scripting vulnerability, an attacker’s script is executed through the user’s browser. Unfortunately, this allows an attacker to obtain sensitive information such as login credentials, timestamps, or personal information. It can also enable other malicious actions, such as manipulating page content, redirecting the user to a malicious website, or infecting the user’s system with malware. The possibilities for danger are endless!
XSS has many layers. Let’s dive deeper into the types of XSS in the next section.
In 2019, a security researcher discovered an apparent XSS vulnerability in Google Translator. This vulnerability allows attackers to inject malicious code into translated text that can be executed by others. Check out this photo below!
Open XSS is a type of cross-scripting vulnerability that occurs when an application reflects user input in a response without proper validation or coding. These attacks often involve the attacker creating a malicious link or form containing a script. When a victim clicks on a link or submits a form, their browser executes the script.
Cross Site Scripting Prevention】protect And Prevent Xss
Let’s say you have an API endpoint that returns a list of articles based on a search query. The server then returns a list of articles containing the title, author, and content of the article in a JSON response. A vulnerable code example that reflects user input without proper encoding or validation:
In this example, the $search_query variable is not cleared or validated and is inserted directly into the JSON response returned to the user, making it vulnerable to an XSS attack. So how does an attacker do the XSS shown here? An attacker can create a malicious URL that contains text as a request parameter. See below:
The victim’s browser runs a script that displays a warning box with an “XSS” message. An attacker can use this to steal the victim’s session cookies, passwords, or other sensitive information or perform other malicious actions. This is dangerous!
Do not worry! You can avoid this by using input validation in your code. How can you sanitize and validate all user input and encode any special characters before entering the response?
In 2018, a security researcher discovered a cross-site scripting (XSS) vulnerability in Snapchat that allowed attackers to inject malicious code at business.snapchat.com. The vulnerability could allow an attacker to steal user data or perform other malicious actions.
Stored XSS, also known as persistent XSS, is a cross-scripting attack in which malicious code is permanently stored in the target application’s database or server. Unlike reflected XSS, where malicious code is injected in response to a user request, a cached XSS attack can affect all users who access the vulnerable page or resource. A stored XSS attack occurs when an attacker is able to submit malicious data to a website, such as a form or comment field, and store it and display it to other users.
Let’s say you have an API endpoint that allows users to post comments on an article. The server then stores the comments in the database and returns them in a JSON response, including the text of the comment and the author. Here is an example of sensitive code that stores user input without proper encoding or validation:
Mastering The Art Of Red Teaming: Advanced Techniques And Strategies For Penetration Testers
In this example, the $comment_text and $author variables are not cleared or changed. They are inserted directly into the JSON response returned to the user, making it vulnerable to cached XSS attacks. An attacker could create a malicious comment containing a script similar to the following:
The URL in the payload points to a web server controlled by the attacker (http://192.168.0.1:8888/) and cookies are included as a query string parameter (?cookies=). is going
What Is Cross Site Scripting (xss) ?
If a malicious web page is injected with a payload and someone visits the affected page, their browser will send a request to the attacker’s server including the session cookie as a parameter. An attacker can then use this cookie to impersonate the victim and perform actions on their behalf within the web application. Account takeover!
Do not worry! You can avoid this by using input validation in your code. Here’s how to sanitize and validate all user input and encode any special characters before storing in the database.
In this case we clear the $_POST[‘comment’] and $_POST[‘author’] variables using the htmlspecialchars function with the ENT_QUOTES and UTF-8 parameters to be interpreted as code by the browser.
In 2022, a security researcher discovered a DOM-based cross-site scripting (XSS) vulnerability in the TikTok advertising platform ads.tiktok.com. The vulnerability allowed an attacker to inject malicious code into the platform’s landing page and execute it in the user’s browser. This could allow an attacker to steal user data or perform other malicious actions.
Xss Attacks: Best Prevention
DOM-based cross-site scripting (DOM XSS) is a type of cross-site scripting vulnerability discovered in the Document Object Model (DOM), which represents web page data in the browser. In a DOM-based XSS attack, the malicious payload is implemented through a simple injection into the HTML source code or by securely modifying a DOM property instead of appearing in the server’s response.
In DOM-based XSS attacks, the payload is often included in the URL or as part of the client code, and is usually executed when the victim interacts with the page in a specific way. For example, a payload can be triggered when a victim clicks a link, submits a form, or enters text into an input field.
However, there are potential vulnerabilities in this code. If an attacker can manipulate the value of the name input field to include a script tag, he can inject malicious code into the page and execute it in the victim’s browser. For example, an attacker could enter the following input:
Xss In Practice: How To Exploit Xss In Web Applications (walktrought Into Google Xss Game) — Stackzero
In this example, the attacker “XSS!” inserts a text tag into the page that displays its text. shows a warning box with
Here, the developer has updated the greet() function to include input validation and output encoding in this example. The input validation step removes script tags from the input field, preventing embedded scripts from executing. The output encoding step prevents any special characters from being interpreted as executable code by using the encodeURIComponent() function to encode the name variable.
It is important to remember that the attack scenarios and code snippets presented above are simple examples for developers to avoid XSS vulnerabilities. In real-world situations, the verification/blocking process can be very complex.
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