At the end of November, hacker and unc0ver lead developer Pwn20wnd shared a Tweet indicating that Substitute — the primary tweak injection method for this particular jailbreak — would soon be updated to version 2.0 with a trove of improvements.

Without any sort of ETA provided at the time, no one could have guessed when Substitute v2.0 would launch. With that in mind, many unc0ver users were taken by surprise late last night when the update officially became available by way of Sam Bingner’s repository.

Citing the official change log for Substitute version 2.0, this release incorporates the following changes:

Changes in Substitute 2.0.0 (1/7/2021)

– Redesigned the injection system to be faster and handle large numbers of tweaks more efficiently
– Validated support for checkra1n as well as unc0ver on any version
– iOS11 through iOS14 supported on compatible jailbreaks
– iOS14 arm64e support added
– Added an App to allow centralized control of Substitute settings
– Added the ability to submit crash logs (opt-in)

While it seems like a sound update at first glance, posts have already started materializing on /r/jailbreak with a common warning that users should avoid installing Substitute v2.0 as of right now, as it seems to be causing instabilities for a handful of users. One reported an unsupported jailbreak popup and being “booted into a non-jailbroken state” with no obvious way to resolve the problem. Other users soon affirmed similar circumstances. The only known solution was to boot into Safe Mode (no tweaks) via the unc0ver app and downgrade to an earlier version.

Subsequently, Substitute v2.0.1 was released early this morning with the following changes:

Changes in Substitute 2.0.1 (1/8/2021)

– NOTE: If you see unsupported jailbreak on new u0 please rejailbreak or run ‘launchctl reboot userspace’
– Fix a bug in the substrate compatibility layer

From what we can gather, the second update provided advice for those facing problems with Substitute after the update. Most notably, those users should re-jailbreak and/or run the ‘launchctl reboot userspace’ command. Some users on /r/jailbreak reported success after upgrading to Substitute v2.0.1 and following the instructions.

If you’re still skeptical with regard to installing the latest version of Substitute, then we’d advise waiting a little longer before upgrading — at least until either Pwn20wnd or Sam Bingner make a public statement about the best course of action or until another Substitute update irons out the issues users have reported.

Have you updated to the latest version of Substitute yet? Let us know how it went for you in the comments section down below.