Apple no longer signing iOS 12.3-12.3.2,
hindering downgrades from iOS 12.4
情报来源：
https://www.idownloadblog.com/?p=743988
Apple is no longer signing iOS 12.3, 12.3.1, or 12.3.2 for its mobile device lineup as of Wednesday evening, a move that prevents users from restoring to any firmware version older than iOS 12.4, which was released to the general public just last Monday.
延伸：
https://ipsw.me
提供想更新、还没更新、想降版本的人以上资讯。
iOS 11 好像还不少人用，
赶快升一升一起来人间吧...。