1. Introduction
Cross-Site Scripting (XSS) is a type of web security vulnerability that allows attackers to inject malicious scripts into websites viewed by other users. This can lead to account takeover, data theft, and website defacement. XSS vulnerabilities typically affect any web application that accepts user input without proper validation or sanitisation. A successful exploit could compromise the confidentiality, integrity, and availability of a system.
2. Technical Explanation
XSS occurs when an application includes untrusted data in its HTML output without escaping it. This allows attackers to inject client-side scripts (typically JavaScript) that are then executed by the user’s browser. If the injected script is immediately returned, this is reflected XSS. Persistent XSS happens when the malicious script is stored on the server and served to other users. Scanner has identified a vulnerability where script content can be directly inserted into HTML element content.
- Exploit mechanism: An attacker crafts a malicious URL containing JavaScript code and tricks a victim into visiting it. When the victim’s browser renders the page, the injected script executes. For example, an attacker could inject `` into a search field parameter.
- Scope: Web applications that accept user input without proper sanitisation are affected.
3. Detection and Assessment
To confirm vulnerability, check if untrusted data is echoed back in the response or stored on the server. A quick check involves examining the HTML source code for unescaped characters. Thorough assessment requires manual testing with various payloads.
- Quick checks: Inspect the URL parameters and page content to see if input appears directly in the HTML.
- Scanning: Use vulnerability scanners like OWASP ZAP or Burp Suite, looking for XSS signatures. These are examples only; results should be manually verified.
- Logs and evidence: Examine web server logs for suspicious characters or patterns in user requests. Look for attempts to inject `