Minecraft 1.7 introduces changes to the world generation code that could very likely result in structures (like strongholds and nether fortresses) generated in 1.6 no longer being recognised as valid. As this would mean that special behaviour for structures would stop working as expected (like wither skeletons spawning in nether fortresses, for example), we felt that it was important to give our Server Admins a heads up.
Minecraft 1.6.4 introduces a new structure saving feature that should ensure that structures generated before 1.7 continue to be recognised as valid structures after updating. If you don't want to lose your structures from 1.6, you need to update to 1.6.4 first and make sure the structures are saved.
What needs to be done
If you're planning to continue running your 1.6 world come 1.7 and want to ensure that structures retain their special behaviour as expected, there is an extra step you need to take as part of the update process....
A new CraftBukkit Recommended Build (1.6.4-R1.0) that provides Minecraft 1.6.4 compatibility is now available. As this new Recommended Build also contains a CRITICAL security fix, updating is HIGHLY recommended.
Notable Changes: Preventing potential structure (stronghold, fortresses, etc.) loss in 1.7
Along with a CRITICAL security fix, Minecraft 1.6.4 also contains a special fix for a problem that could potentially pop up in the future by enabling the saving of generated structures to disk. As such, it is recommended that everyone update to this Recommended Build and explore around the structures you wish to save. For more information on this feature and tips on how to save your structures (as well as a utility you can use to streamline the process), see this announcement.
Re-enabling the built-in auto-save
We've also re-enabled the built-in auto-save by...
A new CraftBukkit for Minecraft 1.6.4 DEVELOPMENT build is now available!
As of this post, we've shifted development over to Minecraft 1.6.4 compatibility and now have development builds available. We strongly suggest that you only use this build if you would like to help us get a Beta build out sooner and are experienced with using unsupported development builds. If you have to ask where or how to get the development build, you should NOT be running it and posts of that nature will be deleted.
WARNING: Minecraft 1.6.4 is an update that requires clients to update before being able to connect.
Will plugins break with this build?
Provided the developers of the plugins you are using are keeping up with the development of Bukkit, all your plugins should work fine. Unless we specifically have to break plugins or the plugins you are using are employing inappropriate practises, most plugins should work without needing an update whenever we put out a new release.
It has come to our attention that the plugins "NanoGuard Anticheat" and "InfiniteDispenser" have been distributing potentially malicious code hidden within their update process. We urge all server admins running these plugins or who have run these plugins to read this PSA carefully and follow the advice given immediately.
We strongly advise all server admins to cease using these plugins immediately:
NanoGuard Anticheat (Default file name: NanoGuardJAR.jar or similar)
InfiniteDispenser (Default file name: InfiniteDispenser-3.2.jar or similar)
As a general precaution, we strongly recommend that all server admins perform a full examination of their server, keeping an eye out for unknown plugins or suspicious behaviour - as is proper on a periodic basis. We also would like to remind server admins to avoid running anything with root or admin privileges without taking the proper precautions to safeguard against the security risks it poses.