Source: cve@mitre.org
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) flaws, allowing attackers to inject malicious scripts into the application. Successful exploitation could lead to account compromise, data theft, and website defacement, impacting the confidentiality, integrity, and availability of the system.
Step 1: Payload Delivery: The attacker crafts a malicious payload, typically JavaScript code, designed to execute within the victim's browser.
Step 2: Input Injection: The attacker injects the crafted payload into one of the vulnerable input fields within SimpleInvoices. This could be through forms for adding users, customers, billers, invoices, or payment types, or through other configuration settings.
Step 3: Data Storage: The injected payload is stored in the SimpleInvoices database, associated with the specific data field it was injected into.
Step 4: Victim Interaction: A legitimate user (victim) accesses a page within SimpleInvoices that displays the data containing the malicious payload. This could be a user profile, invoice details, or any other page displaying the compromised data.
Step 5: Payload Execution: The victim's browser renders the page, and the injected JavaScript payload is executed, as the application fails to properly sanitize or encode the output. This allows the attacker to perform actions in the context of the victim's session, such as stealing cookies, redirecting the user to a phishing site, or modifying the website's content.
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-controlled input from various fields, such as email addresses, customer names, and invoice descriptions, is directly embedded into the HTML response without escaping special characters. This allows an attacker to inject malicious JavaScript code within these fields, which is then executed by the victim's browser when they view the affected pages. The absence of input validation allows malicious payloads to be submitted, and the lack of output encoding (e.g., HTML entity encoding) prevents the browser from interpreting the injected code as data rather than executable script.
While no specific APT groups are directly linked to this specific CVE, the nature of XSS vulnerabilities makes them attractive to a wide range of attackers, from script kiddies to more sophisticated actors. The impact of successful exploitation (account compromise, data theft) aligns with the goals of various threat actors. This vulnerability is not listed on the CISA KEV (Known Exploited Vulnerabilities) catalog, likely due to its age and the fact that it affects a specific, less widely used application.
Web Application Firewall (WAF) logs: Look for suspicious HTTP requests containing common XSS payloads (e.g., <script>, onerror, javascript:).
Server-side logs: Examine server logs for unusual POST requests with potentially malicious data in the vulnerable fields.
Network traffic analysis: Monitor network traffic for unusual JavaScript execution or redirects originating from the SimpleInvoices application.
Vulnerability scanners: Utilize vulnerability scanners to identify instances of SimpleInvoices and check for the presence of this vulnerability.
Content Security Policy (CSP) violations: If CSP is implemented, monitor for violations that may indicate XSS attempts.
Upgrade to SimpleInvoices stable-2012-1-CIS3000 or later. This is the primary and most effective remediation step.
Implement input validation: Sanitize all user-supplied input to remove or escape potentially dangerous characters (e.g., <, >, &, ', ").
Implement output encoding: Encode all output data, especially data that is displayed in HTML, using appropriate encoding mechanisms (e.g., HTML entity encoding) to prevent the browser from interpreting injected code.
Implement a Content Security Policy (CSP): Configure a CSP to restrict the sources from which the browser can load resources, mitigating the impact of successful XSS attacks.
Regularly scan the application for vulnerabilities using automated tools.
Review and harden the web server configuration to minimize attack surface.