This article lists undocumented changes that have appeared in Patch 2.4.2.
- The quest from in Shattrath no longer rewards a upon completion.
- was added to .
- An epic version of the / has been added to / . 
- Cat mounts that are standing still have regained an audible roar when pressing the spacebar.
- enchant text changed from "Mithril Spurs" to "+4% Mount Speed."
- The enchant text for Enchant Gloves - Riding Skill has changed from "Riding Skill" to "+2% Mount Speed."
- The cooldown of Power Circle granted by has been lowered from 2 minutes to 1.5 minute.
- The buff granted by has been renamed to "Disdain" to avoid confusion with the Shaman ability Heroism.
- The Scryer proc on the now has the same sound as a warrior charge.
- The Warrior's Bloodrage and Berserker Rage abilities and the troll Berserking and orc Blood Fury racial abilities have a new sound associated with them. This same sound is also used with shaman's Bloodlust.
- Chat filters have been fixed.
- Lines that wrap in chat frames are now indented all subsequent lines after the first.
- The "Mount" line has been added to the tooltips of all mounts.
- Sending an
\nto chat no longer instantly logs players out.
\rcannot be used to place a newline in your messages. Chat messages will be truncated on these codes. If the resulting message length is 0, and channel is "say", "yell", or "emote" other players will see emotes "<player> says something unintelligible.", "<player> yells at his team members.", or "<player> makes some strange gestures." respectively. In most other channels empty messages will be displayed.
- Players' deaths now correctly appear in the combat log.
- Confirmation messages when looting BoP items that only you can loot are back.
- Spaces are added when a character talks in excess of 1 line, this is to prevent players from impersonating a player.
- Weapon oils placed in a guild bank now show the correct number of charges left.
Lua/XML Changes Edit
Following changes have been made in LUA/XML which would effect macros and addons :
- Constants GOLD,SILVER and COPPER changed to GOLD_AMOUNT, SILVER_AMOUNT and COPPER_AMOUNT 
- GuildRosterSetOfficerNote - escape characters are now strictly evaluated and require escaping 
- Minimap:PingLocation(0,0) is now a restricted function to the Blizzard UI only if you are currently targeting area of effect spell. 
- CombatLogSetCurrentEntry() behavior for negative and zero ids is shifted by 1 position. Newest is at 0 (was at -1), oldest is at -CombatLogGetNumEntries() + 1 (was at -CombatLogGetNumEntries())
- Most if not all constants for plural forms (<CONSTANT_NAME>_P1) are eliminated and singular ones updated to use new "|4" escape sequence for generating plural forms.
- New 6th parameter "addToStart" added to ScrollingMessageFrame:AddMessage. When true, adds new message to the opposite end of the message frame.
Here is another wiki page discussing observed API changes
- and added to Shattrath City, to duplicate and , respectively.
- has been added next to the inn in the Aldor Rise, the NPC offers repairs as well as engineering supplies.
- <Mage Trainer> was added in Theramore, inside the tower.
- Windy Cloud have been fixed so half of the spawns are no longer unreachable.
- Silva Fil'naveth again purges all buffs from a druid when they use the flight path to Rut'Theran Village. May also affect horde druids going to Thunder Bluff via their druid flight path.
- Wretched Devourer now devour 370 mana instead of 1360
- New experimental performance tweak added using a combination of full screen glow and multisampling. Add the line
SET AllowMultisampleFBO "1"to "/Applications/World of Warcraft/WoWTest/WTF/Config.wtf". Results were positive or neutral in limited testing. 
- If you stand far away from an NPC with a blue question mark (to interact with), and you hold your cursor on him, the cursor is now displayed properly. Before it disappeared. The cursor is now the same if you hold your cursor on an NPC with a yellow question mark.
- Tiger mounts now properly make a sound when holding still and pressing the space bar.
- ^ http://forums.worldofwarcraft.com/thread.html?topicId=6440785021&sid=1
- ^ http://code.google.com/p/epgp/issues/detail?id=162
- ^ http://forums.worldofwarcraft.com/thread.html?topicId=6440945725&sid=1
- ^ http://forums.worldofwarcraft.com/thread.html?topicId=6136345365&sid=1