CVE-2026-59259: n8n: External Secrets Permission Bypass via Expression Parser Mismatch

Due to a mismatch between the static validation check and the runtime expression engine, an authenticated user with credential create or update permissions, but without the externalSecret:list scope, could embed external secret references into credentials in forms the validation did not detect. These references would resolve at workflow execution time, exposing secret values the user was not authorized to access.

This issue only affects instances where an external secrets provider is configured and Advanced Permissions are in use.