n8n before 1.123.55, 2.25.7, and 2.26.2 contains an authorization bypass in the POST /workflows/{workflowId}/test-runs/new endpoint, which authorizes access using the workflow:read scope instead of workflow:execute. An authenticated user with read-only access to a workflow can trigger a real evaluation test run, causing the workflow to execute via the internal workflow runner and resulting in unintended outbound API calls, data mutations, or other side effects in connected downstream systems. The issue primarily affects instances using the Evaluations feature where RBAC project roles grant workflow:read without workflow:execute.