新版本的chrome会限制iframe下下载文件，除非在iframe中添加 sandbox="allow-downloads" 属性，否则都会报下面这个错误

Download is disallowed. The frame initiating or instantiating the download is sandboxed, but the flag ‘allow-downloads’ is not set. See https://www.chromestatus.com/feature/5706745674465280 for more details.

但是有些情况下，你不能去修改iframe上层的代码，包括iframe本身。那怎样可以下载呢？可以试试下面这个方法：

/**
 * 通过链接下载文件
 * @param url 文件链接
 */
export const downloadFile = async (url: string) => {
  if (!document || !url) return false

  // 获取文件名用
  const b = document.createElement('a')
  b.href = url

  fetch(url).then((res) =>
    res.blob().then((blob) => {
      const a = document.createElement('a')
      const blobUrl = window.URL.createObjectURL(blob)
      a.href = blobUrl
      a.download = decodeURIComponent(b.pathname?.split('/')?.pop())
      a.click()

      window.URL.revokeObjectURL(url)
      a.remove()
      b.remove()
    })
  )

  return true
}

参考资料：前端复盘: iframe跨页通信和前端实现文件下载