InvoiceShelf is an open-source web & mobile app that helps track expenses, payments and create professional invoices and estimates. Prior to version 2.2.0, a Server-Side Request Forgery (SSRF) vulnerability exists in the Invoice PDF generation module. User-supplied HTML in the invoice Notes field is passed unsanitised to the Dompdf rendering library, which will fetch any remote resources referenced in the markup. This can be triggered via the PDF preview and email delivery endpoints. This issue has been patched in version 2.2.0.