InvoicePlane is a self-hosted open source application for managing invoices, clients, and payments. A Stored Cross-Site Scripting (XSS) vulnerability occurs in the Edit Invoices functions of InvoicePlane version 1.7.0. When editing invoices, the application does not validate user input at the `invoice_number` parameter. Although administrator privileges are required to exploit it, this is still considered a critical vulnerability as it can cause actions such as unauthorized modification of application data, creation of persistent backdoors through stored malicious scripts, and full compromise of the application's integrity. Version 1.7.1 patches the issue.