Which of the following types of jailbreaking allows user-level access but does not allow iboot-level access?

A Bootrom exploit targets the hardware-level read-only boot code, providing the deepest possible access that inherently includes and surpasses iBoot-level control.

An iBoot exploit specifically compromises the iBoot bootloader stage, granting exactly the iBoot-level access the question excludes.

A Sandbox exploit escapes an application's sandboxed environment but is not a recognized jailbreak classification that defines bootloader access tiers.

A Userland exploit targets vulnerabilities in iOS user-space applications or services, granting elevated or root access within the OS without touching the iBoot bootloader or bootrom. Because the secure boot chain below the OS layer remains intact, the attacker cannot perform iBoot-level operations such as loading unsigned kernels at boot time. This makes it the least privileged category of iOS jailbreak.