noun
confusing set-up; puzzling method
Internet slang for a baffling or inexplicable design, specification, or way of doing things, often with a critical or exasperated tone.
このアプリの謎仕様には本当に困っている。
I'm really struggling with this app's baffling design.
また謎仕様のアップデートが来た。
Another update with puzzling changes has arrived.
仕様 means 'specification' or 'way of doing'; 謎仕様 adds a critical nuance that the specification is baffling.
Compound of 謎 (なぞ, 'mystery') and 仕様 (しよう, 'specification, way of doing'). Likely originated as internet slang to criticize confusing software or system designs.