CVE-2009-4534

Step 1: Craft Malicious URL: The attacker crafts a URL that exploits the open redirect vulnerability. This URL will point to the vulnerable Drupal site and include a parameter that controls the redirection destination (e.g., ?redirect=http://attacker.com).

Step 2: Social Engineering: The attacker uses social engineering techniques (e.g., phishing emails, malicious links on social media) to trick a user into clicking the crafted URL.

Step 3: Redirection: When the user clicks the malicious URL, the vulnerable Drupal module processes the request. Due to the lack of input validation, the module redirects the user to the attacker-specified URL (e.g., http://attacker.com).

Step 4: Phishing/Malicious Activity: The attacker's website (e.g., http://attacker.com) can be a phishing site designed to steal credentials, a site that delivers malware, or any other malicious content.

The root cause of CVE-2009-4534 is a failure to properly validate user-supplied input used for redirecting users. Specifically, the FAQ Ask module likely uses user-provided data, potentially from a URL parameter, to determine the destination URL after a form submission or other action. The module does not adequately sanitize or validate this input, allowing an attacker to inject a malicious URL. This allows the attacker to craft a URL that, when clicked by a victim, redirects them to a site controlled by the attacker. The lack of input validation is the core logic flaw.