I was checking Random Minecraft seeds and I found this Giant box in One.
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This type of glitch is known as a chunk glitch. usually caused by closing the game before it can save properly which corrupts the file you can search for more information about it here.
-> https://bugs.mojang.com/browse/MC-89269?jql=text%20~%20%22chunk%20glitch%22
As a temporary fix for this world, you can use the fill command to replace the block with air. a tutorial for that is here