InvoicePlane is a self-hosted open source application for managing invoices, clients, and payments. In version 1.7.2-beta-1, InvoicePlane stores client_email values without enforcing email syntax and renders them unescaped inside double-quoted value attributes in the invoice mailer form and quote mailer form. An administrator who can edit a client can store attribute-breaking input, and, when the mailer is configured, JavaScript executes when another authenticated administrator opens the related mailer page. The script runs in the InvoicePlane origin and can perform same-origin actions with the victim's session. This issue is fixed in version 1.7.2.