Cross-site scripting

Definition

Cross-site scripting (XSS) is a type of security vulnerability where an attacker injects malicious scripts into web pages viewed by users. This exploitation occurs when web applications allow users to input data that gets reflected back to other users without proper validation or encoding, leading to unauthorized actions, data theft, or session hijacking. XSS is a major concern in web security and can significantly impact payment systems and user trust in online transactions.

5 Must Know Facts For Your Next Test

1. XSS vulnerabilities can be categorized into three main types: stored XSS, reflected XSS, and DOM-based XSS, each differing in how the malicious script is delivered and executed.
2. Stored XSS occurs when the malicious script is permanently stored on the target server, while reflected XSS happens when the script is reflected off a web server and executed immediately.
3. DOM-based XSS exploits vulnerabilities within the Document Object Model (DOM) of the webpage, executing malicious scripts directly in the browser without needing a server response.
4. Preventative measures against XSS include input validation, output encoding, and implementing Content Security Policies (CSP) to limit where scripts can run from.
5. XSS attacks can lead to serious consequences, such as account takeovers, unauthorized transactions in payment systems, and leaking sensitive information from users.

Review Questions

• How does cross-site scripting (XSS) exploit vulnerabilities in web applications, and what are some common types of XSS attacks?
  • Cross-site scripting exploits vulnerabilities by allowing attackers to inject malicious scripts into web pages. The most common types of XSS attacks are stored XSS, where the script is saved on the server for future users, reflected XSS, which immediately reflects the script off the server to a victim who clicks a malicious link, and DOM-based XSS, which manipulates the client-side script in the user's browser without direct interaction with the server. Understanding these types helps identify how user input can lead to security issues.
• What role do Content Security Policies (CSP) play in defending against cross-site scripting attacks?
  • Content Security Policies (CSP) serve as a vital security measure to prevent cross-site scripting by allowing developers to specify which content sources are trusted and which are not. By setting strict directives about where scripts can be loaded from or executed, CSP minimizes the risk of loading malicious scripts. Implementing a CSP creates an additional layer of security that significantly reduces the chances of successful XSS attacks against web applications.
• Evaluate the impact of cross-site scripting on user trust and transaction security within online payment systems.
  • Cross-site scripting can severely undermine user trust in online payment systems due to its potential for data theft and unauthorized transactions. When users are targeted through XSS, they may unknowingly provide sensitive information like credit card details or login credentials to attackers. This breach not only affects individual users but can also damage the reputation of businesses involved. Ensuring robust protection against XSS vulnerabilities is essential for maintaining customer confidence and securing online transactions.

Related terms

Script Injection: A technique used by attackers to insert malicious code into a web application, often leading to unauthorized access or manipulation of user data.

Session Hijacking: An attack where an attacker takes over a user's session after successfully obtaining their session identifier, allowing them to impersonate the user.

Content Security Policy (CSP): A security feature that helps prevent XSS attacks by allowing web developers to specify which dynamic resources are allowed to load on their web applications.