This release is just a Security Release (fixing some bugs and exploits), but it is recommended you update, especially if you have a server.

Some details:

“This version is fully compatible with all previous 1.8 versions, but it is still highly recommend to update to 1.8.5 as soon as possible.

[Bug MC-79632] – Phantom Custom Player in Scoreboard / UUIDs of non-player entities on scoreboards truncated after relog
[Bug MC-75630] – Exploit with signs and command blocks
[Bug MC-80478] – Better server validation for movement packets
[Bug MC-80479] – Invalid beacon effects are not validated
[Bug MC-80480] – Certain attribute values are not bound“