Patch 4.1.0 (undocumented changes)

General

 * Damage-dealing knockback abilities will no longer knock the target away if the damage results in a killing blow. This change is likely a workaround for a bug that would often make NPCs killed by knockbacks unlootable without logging out and logging back in.
 * New music added for PvP content.
 * Is it no longer possible to send guild invitations to players who are on trial accounts (an error is generated).

Races

 * Goblin and worgen /roar sounds have been disabled.
 * The Goblin racial Best Deals Anywhere no longer applies for any vendor not affiliated with a faction, such as Roxi Ramrocket and Yasmin.

Druid

 * Swiftmend no longer consumes Omen of Clarity procs.
 * The cooldown of Prowl now starts when the ability is used, instead of when it is cancelled.

Hunter

 * Roar of Sacrifice has a new icon.
 * Pets now auto-level with the hunter.

Paladins

 * Divine Guardian now has an effective range of 30 yards (the tooltip is contradictory).

Priest

 * A Lightwell can no longer be targeted with macros, similar to totems.
 * Penance ticks no longer cause friendly targets to flinch.
 * Mind Sear deals damage to target if hostile instead of just the targets nearby. No change when cast on friendly targets. Can no longer be cast upon yourself.
 * Improved Devouring Plague front end damage can no longer damage mobs such as mechanicals that are immune to diseases. They are now immune to both the DoT and the instant nuke portions of the spell.
 * Shadowfiend damage reduced.
 * Paralysis (priest talent) is now a magic effect and can no longer be dodged or parried. It is still considered a snare and retains those properties.
 * Glyph of Dispel Magic now requires a magic debuff to be dispelled to grant the heal.
 * Shadow Word: Death's backlash is reported to strike sooner.

Rogue

 * The cooldown of Stealth now starts when the ability is used, instead of when it is cancelled.

Dungeons & Raids

 * Maps of Outland dungeons have been added.
 * The meeting stone for Blackwing Descent has moved slightly.
 * In Deadmines, the ceiling of Ironclad Cove has been updated.
 * Al'Akir will now drop random necklaces and cloaks as well as helm or shoulder tokens in addition or in some cases instead of his current loot.
 * The amount of gold dropped from some Burning Crusade raid bosses (such as Magtheridon, Doomwalker, Doom Lord Kazzak) has been reduced by 90%.

Battlegrounds

 * A countdown timer has been added displaying the time until the battle begins.

Items

 * Bone Fragments, Crypt Fiend Parts, Dark Iron Scraps, Core of Elements, and Savage Frond, which became useless in 4.0.3a since they could no longer be turned in for Argent Dawn reputation, are now poor quality (grey) items.
 * Glass Fishing Bobber now functions as a lure.
 * Long Elegant Feather changed from to  quality.

Mounts

 * Flying mounts now state "This is a flying mount." in both the item and spell tooltip.
 * Smaller flying mounts with legs (such as gryphons, wyverns and hippogryphs) can now swim, and have been given ground mount abilities in no-flying areas, or when a player has not yet purchased the required flight training. Comes with appropriate movement animations for swimming and jumping.  This does not include drake/dragon mounts.
 * Engineer flying machines, Tailor flying carpets and rockets can also swim.
 * Other legless mounts such as Mimiron's Head, nether rays, and phoenix mounts cannot.
 * The Winged Steed of the Ebon Blade cannot, but this may be an oversight, or to be implemented in a later patch.
 * All flying mounts can be summoned while at the surface of water, allowing for liftoffs. They are still dismissed though when diving deeper into the water (except the ones that can be a ground mount).
 * Looting Muddy Crawfish for the Orgrimmar daily cooking quest Crawfish Creole no longer dismounts you.

Companions

 * Companions now are resummoned after a login, zone change or other reasons that cause them to despawn.
 * Companions now stealth when your character stealthes or turns invisible.
 * Many companions have new sounds when clicked. Additionally, companions no longer generate constant noise while summoned (examples of companions affected are Lil' Smoky and Disgusting Oozeling).

Achievements

 * added as a Feat of Strength.
 * Two new companion pet achievements added: and.
 * Items disenchanted via the Disenchant loot roll now count towards the Dust, Dust and more Dust! guild achievement (whichever guild the disenchanter is in gets credit).
 * New quest achievements added: and.
 * New achievements for consuming Cataclysm food and drink added: and.
 * New tabard achievement added:.
 * New achievement added for.
 * New achievement added for eating cookies:.

World Environment

 * Dalaran
 * Portals in Dalaran were added back for Stormwind and Orgrimmar.
 * Steam-Powered Auctioneer in Silver Enclave and Steam-Powered Auctioneer in Sunreaver's Sanctuary — now serve anyone instead of engineers.
 * Flying is now allowed.
 * Old Ironforge has been opened.
 * Darnassus has additional Darnassus Sentinels at previously unguarded regions.
 * A long quest chain has been added leading to the reopened Zul'Gurub, beginning with Bwemba in Stormwind City or Orgrimmar.
 * A Shaman trainer named Droha has been added to Darnassus, and Rukua, the Paladin trainer previously standing near Tyrande Whisperwind, has been moved next to him. Both are standing near the portals to Exodar and Blasted Lands and appear to be in a conversation with Elissa Dumas, the Darnassus Portal Trainer.
 * Several goblins who mistakenly had the glowing blue eyes of death knights after the 4.0.3a model update have been fixed. This includes, but is not limited to, Baron Revilgaz and Qizzik.
 * Vassandra Stormclaw no longer has "death knight eyes," and now has a tag indicating her role as a Druid trainer (she had been a druid trainer already).
 * Halduron Brightwing has been given a new outfit.
 * Anvils and forges located in both Alliance and Horde sections of the Temple of Earth in Deepholm are now functional and have proper mouseover tooltips.
 * Marith Lazuria has now moved inside the building she was previously standing outside of.
 * Fungalmancer Glop does not drop loot anymore, despite his tooltip suggesting he still drops Sprinkle of Verlok Miracle-Grow for Through Persistence. (This could of course simply be a bug.)
 * has been moved from an area of Thunder Peak inaccessible by land travel to a new area in the Howling Vale.
 * Shore Crabs are now much smaller, making them easier to identify them as critters.
 * A Verlok Grubthumper at the border of Verlok Stand and Crimson Expanse was moved down a rock so he would not evade unless engaged in melee range.
 * , a rare mob in Azshara who used to be part of the Timbermaw Hold faction, will no longer cause players to lose reputation with that faction when killing him.
 * The Steam Pools are a subzone of Feralas, and not their own zone anymore.
 * Creatures using a version of the "bound/unbound elemental" model (examples: fire, earth, water, air) can now be looted during their death animation more easily, just like other creatures. Previously, the model's hitbox would move up and down during the animation, making it difficult to click it.
 * Alliance Warrior Infantry mobs (objective of The Leftovers (Horde) in Tol Barad) now have the same loot as other Alliance infantry mobs in Tol Barad (They previously dropped no loot, not even coins).
 * Shartuul's Transporter (event) was removed from the game, as well as its precursor quests and items.

Guilds

 * A Guild Charter now only requires 4 signatures in order to become a Guild.

Professions

 * Reagents, patterns and cogwheels are now sold by many more vendors including ones in capital cities. Some professions (such as blacksmithing) require these patterns to reach 525 skill. Previously these items were only available off Twilight Highland vendors and only after doing a quest chain starting at level 84. This effectively reduces the min level required for the relevant professions down from 84 to level 75.
 * The new Cooking and Fishing dailies in Darnassus, Ironforge, Thunder Bluff and Undercity are exclusive with the ones in Orgrimmar and Stormwind and each other, respectively. You can only complete one racial city Cooking and Fishing daily per day.
 * Some recipes which were made unobtainable in 4.0.3a are now taught by cooking trainers (both Horde and Alliance). These recipes are Kaldorei Spider Kabob, Fillet of Frenzy, Tasty Lion Steak and Soothing Turtle Bisque. Some recipes which were previously learned from recipe-items are now also taught by cooking trainers - these recipes are Barbecued Buzzard Wing, Charred Bear Kabobs and Juicy Bear Burger. It also seems the training price for all cooking trainer-recipes, including the proficiency levels, have changed (either slightly increased or slightly decreased).
 * Several Jewelcrafting, Engineering, and Leatherworking recipes no longer require Flask of Mojo and Flask of Big Mojo, which are now poor quality (grey) items.
 * Arcane Bombs now have a lower chance to work on any player higher than level 60.

Archaeology

 * The progression bar for research projects has been set back in place, having been accidentally shifted to the left in the last patch.

Enchanting

 * When in a dungeon group with a character that has leveled enchanting, the chat screen will print out "[name of item] has been disenchanted for loot by [name of player with Enchanting]" upon anyone in the group winning a disenchant roll.
 * Formula: Enchant Weapon - Crusader is once again obtainable (drops from Scarlet Archmage).
 * Formula: Enchant Weapon - Icy Chill appears to be removed from the game.

Engineering

 * Khorium Power Core now only requires 1 Khorium Bar (Down from 3).
 * Renamed "Flying Machine Control" to Flying Machine.
 * Renamed "Turbo-Charged Flying Machine Control" to Turbo-Charged Flying Machine.

Herbalism

 * Lifeblood (herbalism ability) no longer triggers a short cooldown on trinkets with a use effect and the other way around.

Tailoring

 * Admiral's Hat no longer requires Long Elegant Feather.

User interface

 * Shaman characters now have a totem displayed on the right on the character select screen.
 * COMBAT_LOG_EVENT_UNFILTERED has a new argument inserted on 5th place, named "hideCaster".
 * Character Stats, Titles and Equipment Manager are placed under tabs at the right in the Character frame.
 * Drop down box for guild rank demotion/promotion added.
 * On the Blizzard Launcher, the patch completion alert and PLAY button sounds have been changed.
 * Worgen characters can no longer change from one form to another using /transform, and the CanTransform API call has been removed for reasons unknown.
 * The open all bags bind no longer works with bank bags.
 * All alt-codes and special characters can now be used in chat.
 * Switching talent specs now uses a different sound effect.
 * You can no longer /dance while in combat.
 * The authenticator prompt is no longer on the main login screen. This was an intentional change to prepare for future authentication functionality.
 * This change also completely broke the well-known Man-In-The-Middle (mpcor.dll) keylogger for users with an authenticator.
 * Guild reputation is now displayed at the top of the reputation window instead of the bottom.
 * Rated Battlegrounds have been added to the raid browser.
 * The help window has been given an overhaul. The Knowledge Base now sorts topics by subject. "Report Abuse" and "Account Security" buttons have been added.
 * Pending GM tickets are now displayed on the help window button instead of at the top of the screen.
 * Random name generation on the Character Creation screen will now only suggest names that are presently available on the chosen server.
 * Target and focus icons will not appear on the minimap in relation to players of the opposite faction; only NPCs and friendly players can be tracked in this manner.
 * The Maelstrom now has its own loading screen.

Game Engine

 * Added the LAA (Large Address Aware) flag to WoW. This allows systems running a 64 bit Operating System to allocate up to 4GB of RAM to WoW to prevent crashes.  Mainly this was to fix the issue where users with multiple monitors would consistently crash from hitting the 2GB application limit.  The only way to prevent this crash (prior to 4.1) was to manually add the LAA flag, breaking WoW's EULA (specifically 2 E) in the process.  Adding this fix relieved users of the fear that they'd have their account actioned for manually adding the LAA to stop the crashing, despite a Blizzard employee stating in December 2010 that Blizzard wouldn't action accounts for making this change.

Launcher

 * Beginning with 4.1, Blizzard does a Speed Test to 3 distribution servers to determine the user's internet speed to each, then picks the server with the highest download speed to the user. This should result in users' speeds for downloading patch data to increase.  Unfortunately, if the internet speed is too slow, Akamai servers will refuse to send patch data.

Bug Fixes

 * Fixed a bug that caused all Treants to display the same skin.
 * Fixed a bug that prevented players without the Wrath of the Lich King expansion from obtaining the Darkshore quest, The Emerald Dream.
 * Fixed a bug preventing Alliance players from using 's portals in Arcane Pinnacle, Azshara.
 * Fixed a bug causing the camera for Nether Ray mounts to move upon mounting and flying.
 * Fixed a bug that caused some players to disconnect during the quest Fade to Black.
 * Fixed a bug afflicting battleground queues.
 * The reins on the Deathcharger and Crimson Deathcharger no longer extend in front of the mount's face.

Possible bugs

 * Far Sight, Mind Vision, and Eagle Eye cannot be canceled by jumping.
 * Baradin Foxes are as small as critters.
 * The mounts of the questgivers in Tol Barad don't use the flying animation anymore and appear to be standing in the air. Petty Officer Chulok's mount in Tol Barad Peninsula does not fly anymore as well, but stands on the ground, maybe the intended behavior.
 * Troll players on the Kor'kron Annihilator mount now hold their banner as a jousting spear.
 * The Mac client now updates time stamps on files in the Data directory every time the client is used, causing Time Machine to perform unnecessary backups.
 * Join as Group function does not always work for Tol Barad.