Plane is an open-source project management tool. Prior to 1.4.0, Plane exposes the workspace-scoped GET /api/assets/v2/workspaces/{workspace_slug}/download/{asset_id}/ endpoint for project-bound FileAsset objects without enforcing access to the asset's owning project. An authenticated user who belongs to the same workspace, is not a member of the victim's secret project, and knows the target asset UUID can receive a 302 redirect to a signed download URL. The intended project-scoped route for the same asset correctly returns 403. Confirmed affected project-bound asset types are ISSUE_ATTACHMENT, COMMENT_DESCRIPTION, PAGE_DESCRIPTION, and PROJECT_COVER. This bypass exposes private file content protected by the secret project boundary. This issue is fixed in 1.4.0.