1. Introduction
WebChat XSS is a cross-site scripting vulnerability in the remote CGI component of web chat software. An attacker can inject malicious JavaScript code into the system, typically by creating a user account with a crafted email address. This allows them to steal cookies from legitimate users visiting the web chat interface. A successful attack could compromise confidentiality through cookie theft and potentially lead to session hijacking.
2. Technical Explanation
The vulnerability occurs because the web chat module does not properly sanitise user-supplied input, specifically email addresses. This allows an attacker to inject JavaScript code which is then rendered in the profile page of the newly created user or on the ‘lost password’ page when accessed by other users. The Common Weakness Enumeration (CWE) identifier for this issue is CWE-20: Improper Input Validation.
- Root cause: Lack of input validation and output encoding in the web chat CGI script, specifically regarding user email addresses.
- Exploit mechanism: An attacker creates a new user account with an email address containing JavaScript code (e.g., ``). When another user views this profile or requests a password reset for that account, the injected code executes in their browser.
- Scope: Web chat applications using vulnerable CGI scripts are affected. Specific versions were not provided.
3. Detection and Assessment
Confirming vulnerability requires checking the web chat module’s input handling. A quick check involves reviewing the user creation process for email address validation. Thorough assessment includes attempting to create a user with a malicious payload in the email field.
- Quick checks: Examine the source code of the user registration page or use browser developer tools to inspect network requests during account creation.
- Scanning: Nessus vulnerability ID 316173 can identify this issue, but results should be manually verified.
- Logs and evidence: Check web server logs for suspicious characters in email address fields during user registration attempts. Look for patterns like `