source: https://www.securityfocus.com/bid/56882/info
Simple Invoices is prone to multiple HTML-injection vulnerabilities and a cross-site scripting vulnerability because it fails to properly sanitize user-supplied input before using it in dynamically generated content.
Successful exploits will allow attacker-supplied HTML and script code to run in the context of the affected browser, potentially allowing the attacker to steal cookie-based authentication credentials or control how the site is rendered to the user. Other attacks are also possible.
[http://]www.example.com/simpleinvoices/index.php?module=invoices&view=manage&having=%3C/script%3E%3Cscript%3Ealert%28%27POC%20XSS%27%29;%3C/script%3E%3Cscript%3E