CVE-2017-12811

Step 1: Payload Delivery: An attacker crafts a malicious payload containing JavaScript code (e.g., <script>alert('XSS')</script>) and submits it as a rating item's data, such as the rating's title or description.

Step 2: Data Storage: The vulnerable script fails to sanitize the input. The malicious JavaScript payload is stored in the application's database along with the rating item's other data.

Step 3: User Interaction: A legitimate user views the rating item. The script retrieves the rating item's data, including the attacker's malicious payload, from the database.

Step 4: Payload Execution: The script displays the rating item's data, including the unsanitized JavaScript payload, within the user's browser. The browser interprets the JavaScript code and executes it, triggering the XSS attack. This could involve stealing cookies, redirecting the user, or other malicious actions.

The vulnerability stems from insufficient input validation and output encoding within the PHPJabbers Star Rating Script 4.0. Specifically, the script fails to properly sanitize user-supplied input when a rating item is created or updated. This allows an attacker to inject arbitrary HTML and JavaScript code into the rating item's data. When other users view the rating item, the malicious JavaScript executes within their browsers, leading to the XSS attack. The root cause is a lack of proper input sanitization and output encoding (e.g., HTML entity encoding) of user-provided data before it is stored in the database and subsequently displayed. This allows the attacker to inject malicious code that is then executed in the context of other users' browsers. The absence of these security measures allows for the injection of malicious code, leading to the exploitation of the XSS vulnerability.