Devices with the checkm8 bootrom vulnerability (iPhone X and older) can sometimes use special tools to downgrade, but this is complex and often requires specific, limited paths.
Extracting SHSH 11.2.6... Blob contains: "Daddy, I took this picture of a squirrel!" [AUDIO HASH]
SHSH blobs are the digital locks that prevent unauthorized downgrades on iOS devices. For users, saving them is a crucial preemptive action to maintain freedom over their device’s software. Whether you're waiting for a new jailbreak or simply want the security of being able to return to a stable iOS version, taking a few minutes to save your blobs is highly recommended.
Once a version is unsigned, Apple will no longer issue the required SHSH blob for it. Without this signature, the installation cannot proceed through standard methods.
Years later, when his daughter asked why he kept four identical, broken iPhones in a lockbox, he just smiled.
BlobSaver is a popular, cross-platform tool (Windows, Mac, and Linux) that simplifies the process.