Template:ParallelAsynchronousThreadBlock

Word Tearing via Asynchronous Threads
From 14w32a (1.8 snapshot) to 17w46a (1.13 snapshot), asynchronous block updates allow for block palette corruption, and this corruption, when combined with the registry palette type, can allow for the creation of any block that can exist, such as. The hashmap palette also allows for the copying of blocks that already exist within the subchunk, allowing for duplication. These exploits may be also used to create a falling block entity of any block, allowing for it to be duplicated and placed multiple times, as well as allowing placement in future versions.

These illegal falling blocks may also be used to obtain their respective item, if it exists in item form, such as end portal frames. Blocks such as nether portals will not be able to be obtained as items with this method. Falling blocks also bypass any placement restrictions when landing, allowing for the placement of both blocks that cannot normally be placed (e.g. command blocks), and those that cannot be placed in a specific location due to placement requirements (e.g. chests).