Here's a list of undocumented Patch 2.4.2 changes: 

General

• Human Female weapons are bigger, they now match the size they are when sheathed.
• Male Blood Elf Rogues have had their animation improved while stealthed.

• There is still a bug with Growl that is allowing it to scale with some pet attack power buffs as well as the hunter's attack power. This will be fixed in a future patch.
• Scare Beast still has a 1.5 second cast time, and is not instant as indicated on the tooltip. The tooltip will be corrected in a future patch.
• Water Elementals now leave a corpse behind when they despawn (Probably a bug). The corpse is not resurrectable.

• Alliance Mage trainer, Horace Alder, has been added. He is located in Theramore's tower on the floor below Jaina Proudmore. The new Portal trainer, Ysuria is on the ground floor.
• The new Portal Trainer, Lorrin Foxfire, is located on the ground floor of the large building in the middle of Stonard.

• Using the Fel Siphon at Kil'Jaeden's Throne for the quest Blood for Blood will now break a Sap if one is applied to the target.

• Fixed bug where it was possible to kill people with the Fire Nova Totem by logging out as it's exploding.

• Players are no longer rewarded with a Shattered Sun Supplies upon completion of the quest The Multiphase Survey, the reputation from this quest has also been reduced from 250 to 150.

• Stratholme
  Abominations (Bile Spewers and Venom Belchers) at Slaughter Square no longer fall under the ground.

• Heroic Underbog
  The farmable chest in the instance has been removed

• Battle of Mount Hyjal
  Archimonde's hitbox has been increased
  Fire will now target melee players
  Archimonde's doomfire is now able to turn 90 degrees at any given moment.

• Black Temple
  Supremus drops a lot more volcanoes now

• Sunwell Plateau
  Kalecgos no longer resets when you pull him out of the circular platform he is on. However, he can still be reset by pulling him all the way down the hall to the gazebo/room.

• The tooltip for the enchant associated with Mithril Spurs now says "+4% Mount Speed"
• Shaani, Jewelcrafting supplier on the Isle of Quel'Danas now sells Design: Purified Shadowsong Amethyst.
• Officer Accessories Quartermasters in Stormwind and Orgrimmar now sell an epic quality Medallion of the Alliance and Medallion of the Horde respectively. They cost 40k Honor to purchase.
• The price of the rare "Medallion of the Alliance" and "Medallion of the Horde" has been reduced to 8k Honor.

• The combat log now shows players' deaths again
• Chat filters now work correctly
• Sending an \n to chat now results in an emote being sent instead: " <player> says something unintelligible.". This no longer logs players straight out. </player>
• Minimap Ping Macros Disabled - Allowing AddOns to target spells via the minimap ping was not intentional and was fixed. AddOns may not directly cast spells or change targeting.
• Chat interface now indents all lines after the first one on multi-line messages.
• Confirmation messages when looting BoP items that only you can loot are back.

• The abilities Bloodrage, Shamanistic Rage, Bloodfury and Berserker Rage have a new sound, which matches the sound for the Shaman spell Bloodlust/Heroism; this is also the sound some mobs have when they enrage.
• Cat mounts now roar when the spacebar is pressed

• Windy Clouds have been fixed to make sure they can all be reached.
• An NPC has been added to the Aldor Rise, next to the inn. Technician Halmaha offers Engineering supplies and repairs.
• Ontuvo, a Jewelcrafting Supplies sales person, and Anwehu, a Weapon and Armorsmith have been added to Shattrath.