Apple on Wednesday stopped signing both iOS 10.3.3 and iOS 11.0, the first official public release of iOS 11 since the software came out of beta on September 19th. With this change, it's now impossible to downgrade iOS 11 devices back to iOS 10.
The company regularly stops signing older firmware versions to prevent downgrades and keep users on the latest firmware possible. It’s also a measure to thwart jailbreaking, which often requires an older firmware version where Apple hasn’t patched the vulnerabilities used in the jailbreak process.
