Plane: Project Member can escalate Project Guest to Member via PATCH /project-members/{pk} (BAC / Privilege Escalation)

Plane is an open-source project management tool. Prior to 1.4.0, a Project Member with role 15 can send a PATCH request to the project-member update endpoint at /api/workspaces/{workspace_slug}/projects/{project_id}/members/{member_pk}/ to change another user's project role. The role-update logic blocks only a new role higher than the requester's role, so assigning the equal Member role bypasses the insufficient validation and promotes a Project Guest with role 5 to Member without Project Admin approval. This unauthorized promotion grants the guest the additional project capabilities associated with the Member role and allows a regular member to bypass project governance controls. This issue is fixed in 1.4.0.