On servers, client will assume certain actions have been carried out without clarification, for example:

• If player is not allowed to place or break blocks, when they try it will appear client-side for about half a second. This is probably the most important part of this bug as it always you to exploit it and transverse tall walls by spam placing the block underneath yourself.

• Item stacks in an inventory will appear picked up even if the server has denied the ability to take it from the inventory screen. This is frustrating for Bukkit plugins as some inventory can be used for a sort of menu whereby you click a certain item, which will then do a certain action, for instance a shop. This glitchy behavior makes these sorts of menu hard to work with sometimes and makes them look unprofessional (as its the only way of doing because of a lack of server-side defined GUI elements.)

Could you please look into preventing the client from making these presumptions and sometimes confusing itself.