InvoicePlane: Incomplete Authorization Remediation in Users::form() Enables Primary Administrator Account Takeover via Email Reassignment and Password Recovery

InvoicePlane is a self-hosted open source application for managing invoices, clients, and payments. In version 1.7.2, an authorization guard to Users::change_password(), was added to address a previous authorization flaw that allowed a secondary administrator (user_type=1, user_id != 1) to directly change the password of the primary administrator (user_id=1) through users/change_password/{id}. That remediation, however, protects only the direct password-change operation. It does not protect the identity attribute that password recovery actually trusts: user_email. Users::form() applies no equivalent object-level authorization check when editing the primary administrator's account, and user_email is not included in PROTECTED_FIELDS. A secondary administrator can therefore rewrite the primary administrator's email address, then drive the public password-recovery flow — which resolves the account by user_email — to receive the reset token and take over user_id=1. The result is an alternate attack path that achieves the same impact PR #1638 was intended to prevent: cross-administrator full account takeover of the primary administrator. This issue has been patched via commit 8616fa4.