Multiple cross-site scripting (XSS) vulnerabilities in SimpleInvoices before stable-2012-1-CIS3000 allow remote attackers to inject arbitrary web script or HTML via (1) the having parameter in a manage action to index.php; (2) the Email field in an Add User action; (3) the Customer Name field in an Add Customer action; the (4) Street address, (5) Street address 2, (6) City, (7) Zip code, (8) State, (9) Country, (10) Mobile Phone, (11) Phone, (12) Fax, (13) Email, (14) PayPal business name, (15) PayPal notify url, (16) PayPal return url, (17) Eway customer ID, (18) Custom field 1, (19) Custom field 2, (20) Custom field 3, or (21) Custom field 4 field in an Add Biller action; (22) the Customer field in an Add Invoice action; the (23) Invoice or (24) Notes field in a Process Payment action; (25) the Payment type description field in a Payment Types action; (26) the Description field in an Invoice Preferences action; (27) the Description field in a Manage Products action; or (28) the Description field in a Tax Rates action.
SimpleInvoices versions prior to stable-2012-1-CIS3000 are vulnerable to multiple cross-site scripting (XSS) attacks. These vulnerabilities allow attackers to inject malicious JavaScript into the application, potentially leading to account compromise, session hijacking, and data theft by tricking users into executing the injected code within their browsers.
Step 1: Payload Delivery: The attacker crafts a malicious payload (JavaScript code) designed to exploit the XSS vulnerability. This payload is typically embedded within HTML tags.
Step 2: Input Injection: The attacker injects the crafted payload into one of the vulnerable input fields within SimpleInvoices. This can be achieved through various means, such as directly entering the payload into a form field or exploiting a vulnerability in another part of the application to inject the payload.
Step 3: Data Storage (if applicable): The injected payload, along with the user-provided data, is stored in the application's database or configuration files.
Step 4: Victim Interaction: A legitimate user accesses a page within SimpleInvoices that displays the attacker-controlled data. This could be a page listing customers, invoices, or other data.
Step 5: Payload Execution: The victim's browser renders the HTML, including the attacker's injected JavaScript. The browser executes the JavaScript, allowing the attacker to perform actions on behalf of the victim, such as stealing cookies, redirecting the user to a malicious website, or modifying the content of the page.
The root cause of these vulnerabilities lies in the lack of proper input validation and output encoding within SimpleInvoices. The application fails to sanitize user-supplied data before displaying it on web pages. Specifically, user-provided data from various input fields (e.g., email addresses, customer names, invoice descriptions) is directly rendered in the HTML output without escaping special characters. This allows an attacker to inject malicious JavaScript code within these fields. When a legitimate user views a page containing the injected code, their browser executes the attacker's script, leading to the exploitation of the vulnerability.