We had reported yesterday that the untethered jailbreak for iOS 4.2.1 by Comex may not be released before Christmas.

But iPhone Dev team is on track and has announced that it is planning to release a new version of Redsn0w that implements the “backup plan” for iOS 4.2.1 untethered jailbreak over the Christmas weekend.

However, before Redsn0w is released to the public, it is looking for testers to check out the latest version of Redsn0w. iPhone dev team has issued the following statement:

Over the Christmas weekend we’ll be releasing a version of redsn0w that implements the “backup plan” to the 4.2.1 untethered jailbreak.  We’re seeking your help to test this redsn0w and find any bugs before we do a general release!

(If you have an iPhone 3G, or an old-bootrom ipt2g or iPhone 3GS, you already have an untethered jailbreak!  Just use the latest public redsn0w.)

To keep things manageable, this will be a Mac-only test program.  We also request that any volunteers *NOT* need the ultrasn0w unlock (in case things go very wrong).

Right now, the “backup plan” requires that you have the 4.2b3 IPSW on yourMac, and that Cydia has your 4.2b3 SHSH hashes.  Please don’t pirate that 4.2b3 IPSW!  (We’re also working on a way that this technique might apply to all those with 4.1 IPSWs, but that’s not the first goal right now.)

If you fit all the above qualifications, please follow @redsn0w_testers ontwitter for announcements, and use the comments section here for feedback. Thanks very much for your help, and Happy Holidays!

As always, we’ll let you know as soon as the new version of Redsn0w is released so stay tuned here at iPhone Hacks or follow us on Twitter or subscribe to our RSS feed.