CVE-2017-17993

Step 1: Payload Delivery: The attacker crafts a malicious URL containing a JavaScript payload within the amount parameter. This payload is designed to execute arbitrary code within the context of the vulnerable application. For example: index.php?user=addition_deduction&amount=<script>alert('XSS')</script> Step 2: Request Submission: The attacker sends the crafted URL to a victim, typically via phishing, social engineering, or by embedding it on a malicious website. Step 3: Server Processing: The vulnerable Biometric Shift Employee Management System receives the HTTP request. Step 4: Vulnerable Code Execution: The application processes the request, retrieves the amount parameter, and incorporates it into the HTML response without proper sanitization or encoding. Step 5: Browser Rendering: The victim's browser receives the malicious HTML response, including the injected JavaScript payload. Step 6: Payload Execution: The browser executes the injected JavaScript code, allowing the attacker to perform actions such as stealing cookies, redirecting the user, or defacing the website.

The root cause is a failure to properly sanitize user-supplied input before rendering it in the application's response. Specifically, the index.php?user=addition_deduction endpoint likely takes the amount parameter and directly incorporates it into the HTML output without any encoding or filtering. This allows an attacker to inject arbitrary HTML and JavaScript code. The lack of input validation and output encoding is a classic example of an XSS vulnerability. The specific function or logic flaw lies within the handling of the amount parameter, where the application fails to escape or sanitize the user-provided data before displaying it on the page. This allows for the injection of malicious scripts, which are then executed by the victim's browser.