Vulnerability Advisory : InvoicePlane: Guest user IDOR in quote approval and rejection with LOW Attack Complexity

InvoicePlane is a self-hosted open source application for managing invoices, clients, and payments. Prior to 1.7.2-beta-1, guest users can approve or reject quotes belonging to any client, not just their assigned clients. The `approve()` and `reject()` methods in the Guest Quotes controller, `application/modules/guest/controllers/Quotes.php`, call `approve_quote_by_id($quote_id)` and `reject_quote_by_id($quote_id)` directly without the `where_in('ip_quotes.client_id', $this->user_clients)` scoping that sibling methods use. A guest user assigned to one client can change another client's quote status by supplying sequential integer `quote_id` values, and `email_quote_status()` also sends notification emails. Additionally, `generate_pdf()` calls `mark_viewed($quote_id)` before checking the client scope, allowing a guest user to mark another client's quote as viewed. These issues are fixed in version 1.7.2-beta-1 and the subsequent stable version 1.7.2.