$ cat writeup.md…
$ cat writeup.md…
CACTF2026
Task: a 221-byte .mpy artifact that `file` calls 'data' is MicroPython v6.3 bytecode implementing a check function `judge(syllable)`. Solution: fingerprint the magic header, disassemble with MicroPython's mpy-tool.py, reconstruct the rolling XOR/add check, and invert it deterministically to recover the accepted input.
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$sign in$ grep --similar