Unraveling Cross-Site Scripting (XSS) Attacks: Types and Countermeasures

a) What is cross-site scripting (XSS)?

Cross-site scripting attacks (XSS) involve hackers executing malicious JavaScript in a victim’s browser, unlike remote code execution (RCE) attacks. The attacker attaches their code to legitimate websites, tricking the browser into executing their malware when the website loads, unlike RCE attacks where the site is not fully controlled.

b) How do cross-site scripting (XSS) attacks work?

An attacker can inject their own code into a web page, exploiting a vulnerability in the website’s software and allowing them to execute a script on the victim’s browser. This can steal sensitive user information, allowing attackers to target site administrators and compromise the site. Cross-site scripting attacks can also target visitors by adding ads, phishing prompts, or other malicious content.

c) How to prevent cross-site scripting attacks?

To prevent cross-site scripting (XSS) attacks, organizations should implement comprehensive security measures. These include sanitizing user input, using safe coding practices, adopting a Content Security Policy, regularly updating frameworks, libraries, and plugins, educating developers about XSS risks, conducting daily security training, and implementing HTTPS. These measures can significantly reduce the likelihood of XSS attacks and enhance the overall security of web applications.

d) What are the types of cross-site scripting (XSS)?

1. Store (persistent) cross-site scripting

Stored cross-site scripting attacks involve an attacker storing their payload on a compromised server, causing the website to deliver malicious code to other visitors. This method is the most dangerous and commonly used type of cross-site scripting due to its initial action requirement.

2. Reflected (non-persistent) Cross-Site Scripting

Reflected cross-site scripting attacks store payloads in data sent from the browser to the server, a common tactic in phishing and social engineering attacks. These attacks exploit vulnerabilities in websites, providing attackers with a steady stream of legitimate-looking sites for attacks. Examples include search forms where visitors only see the results and custom links directing victims to vulnerable pages.

3. Self Cross-Site Scripting

Self cross-site scripting is a vulnerability exploited by attackers that requires specific context and manual changes, with the only victim being the user themselves, potentially setting cookie values or setting personal information as the payload.

4. Blind Cross-Site Scripting

Blind cross-site scripting attacks are where the attacker cannot see the attack results and are typically located on a page only accessible to authorized users. This method requires more preparation and requires more preparation. Hackers often use polyglots to increase the success rate of these attacks, which can be used in attributes, plain text, or script tags.

5. DOM-Based Cross-Site Scripting

DOM-based cross-site scripting attacks exploit the vulnerability of the server’s JavaScript on the page, allowing attackers to modify the page after loading without sanitizing user-derived values, thereby allowing them to add malicious code without sanitizing the server itself.