Bukkit

5.6.1 didn't block splash potions very well, so 5.6.1 was released. The following are the changes between 5.6 and 5.6.2.

• Added a mycelium-spread region flag.
• Added a dynamics.disable-mycelium-spread configuration setting.
• Added new gameplay.block-potions option. For example:

  gameplay:
      block-potions: [invisibility, speed]
  

• Fixed a bug in the entity explosion event handler that caused a NullPointerException.

Thank you for gabizou for his contribution in this release.

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Did you update from a version older than 5.6? Here's what was new in 5.6:

• Added official support for Minecraft 1.4. Support for 1.3.2 (and below) is still provided in this release.
• Added support for new and existing explosion types.
• Added support for blocking withers with the following settings:

  mobs:
          block-wither-explosions: false
          block-wither-block-damage: false
          block-wither-skull-explosions: false
          block-wither-skull-block-damage: true
  

• Added support for blocking item frames (and their use) in protected regions.
• Added item frame destruction region flags (if you wish to disable item frame destruction completely).
• (Re-)added support for priority R-tree region indexes. This means quicker region lookup, and better support for servers with thousands of regions.
• Improved /region info output for -g group flags.
• Allowed removing of -g group flags with /region flag.
• Allowed /region flag to set group and value at once.
• Deleting a region flag now also deletes group flag.
• Fixed detection of attack by projectiles to be more accurate.
• Fixed support for saving non-string flags in the MySQL region support.
• Fixed spurious comma in "Flags:" /region info output.
• Fixed players who are not in god mode not receiving damage in PVP areas from enderpearls.
• Players will now be told that they are in a no-PvP area if they are in one and attempting to attack someone, or that the player they are attacking is in a no-PvP area, if that is the case instead.
• Fixed an issue where region.getId() was lowercase'd each pass of a for loop in MySQLDatabase.updatePoly2dPoints().
• Fixed mob damage from projectiles not being properly blocked in regions whereapplicable.
• Changed default region wand to leather (#334).

Warning: You should update WorldEdit to the latest version.

Warning: If you are using MC 1.4.2, you should update CraftBukkit to the latest version.

If you want to block Withers spawning, use "WITHERBOSS" and not "WITHER".

Known issues: http://youtrack.sk89q.com/issues/WORLDGUARD?q=%23Bug+Affected+versions%3A+5.6.2