The 2.8.4 update adds new Every Soldier a Sensor training and co-op missions, along with a variety of bug fixes. The changelog for the new version follows:

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What's new
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New ES2 Training & Co-op missions
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ES2 MOUT McKenna (Training)

"Every Soldier a Sensor (ES2) is a potential information collector and an essential component to help reach situational understanding. Every Soldier develops a special level of situational awareness simply due to exposure to events occurring in their Area of Operations (AO) and has the opportunity to collect information by observation and interaction with the environment and the population. The increased situational awareness that soldiers develop through personal contact and observation is a critical element of the Brigade and Battalion's ability to more fully understand, react to, and control the operational environment.

On today's battlefield, information dominance is crucial and the soldier is the Commander's most valuable weapon. By diligently observing the environment the soldier will be able to identify and report objects, people and events which contribute to Command's full understanding of the AO. Things worth reporting include objects which are dangerous or seem out of place, people who are behaving in a suspicious manner, and things which are obviously related to enemy activity (such as weapons, explosives and uniforms). As information is being reported by all soldiers, Command may then be able to put together seemingly disparate information to attain a more complete view of the AO and will be better able to direct soldiers in the field."

The McKenna MOUT site is the location where training in the concept of Every Soldier a Sensor will occur. Players must use key clues to find an IED cache while engaging enemy targets in a timed environment. A Go or No-Go will be given based on number of suspicious objects observed and reported, time of completion, and number of enemy targets engaged. Successful completion of the ES2 training will allow players to accrue points for observing and reporting suspicious objects within the ES2 Border Co-operative Multiplayer level.

ES2 Border (Multiplayer Co-Op)

"Intelligence has identified this small border village as a hotbed for hostile activity and the likely source of IEDs used in recent attacks. The local population is a mix of insurgents, sympathizers and pro-democracy civilians. The sprawling village borders a highway which will be used increasingly in the coming months for friendly troop and supply transport. It is imperative that the insurgency here is addressed with as little negative impact as possible on civilian infrastructure and that any IED related activity be eliminated."

This version of the Border level hosts a co-operative mission where a small village area with low hills is home to an armed group of insurgents. Teams are encouraged while on patrol to be on the lookout for suspicious objects which may lead to clues about current activity within the village.

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What's Fixed
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NOTE: This list only includes bugs present in v2.8.3.1 that have been fixed. Bugs fixed related to new v2.8.4 features and certain security/exploit fixes have been removed from this list.

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Map Specific
- SF Floodgate: Fixed a bug that causes players to spawn in amidst the wrong team.
- SF Floodgate: Added several blocking volumes around AC units on upper level to keep players from accessing exploit areas and to remove areas where player may become stuck.
- River Village: Fixed player blocking volumes so that players can no longer get on top of the AC units.

Miscellaneous
- Fixed a bug that prevents Weapon from coming back from the low ready position after sprinting
- Fixed a bug that showed incorrect Weapon FOV after weapon swap
- Fixed a bug that caused player to be unable to sprint after throwing a grenade while in scoped view.
- Fixed a bug that allowed a player to be able to select a grenade while firing
- Fixed a bug that causes an M4 with reflex sight to have a brief frame pop when player goes into zoom mode
- Fixed a bug that prevents M4 from coming back up after left-clicking while going up a ladder
- Fixed a bug that allowed players to jump higher than allowed aka 'superjump'
- Fixed a bug that was preventing a death message from being seen when killed by the Medevac Chopper's Rotor Blades
- Fixed Ingame Ban System

UI/HUD
- Fixed a bug that prevented carriable objectives from showing on the HUD when a weapon is shouldered.
- Fixed a bug that caused all text to disappear in dead chat after using Commo binds.
- Fixed an AA MBS filter bug causing bullets to not stick
- Fixed a bug showing incorrect points on player scoreboard on Forceclassed servers.
- Fixed a typo in forceclass disabled notification message. Also fixes demorectogglesound (and muzzle flash) so displayed console message matches true state.
- Fixed a bug on AA MBS Filter for Minimum Honor that does not return desired result

Improvement
- AI improvements for hearing and improvements to network and CPU usage for
non-relevant AI
- Improved distance calculations used in hearing to reduce # of
calculations necessary.
- Disabled the delayed start on coop maps.
- Improvements to AI grenade throwing logic - much more accurate distance calculation, new logic that considers new calculation when deciding to throw, reduced min distance to just outside of frag damage radius, and adjusted aiming logic so AI should be better at grenades but still far from perfect (have +/- 5m max distance for distances less than max throw distance).
- Adjusted AI cover seeking logic to better handle selecting from multiple available cover locations