// REFERENCE

DOCX/XLSX/PPTX signature

Signature (hex): 50 4B 03 04 (PK, ZIP) Medium risk

Modern Office documents (OOXML) are ZIP: they start with 50 4B 03 04. The extension isn't enough to tell a DOCX from a ZIP; you must look inside. They can also carry macros (.docm).

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Signatures verifiable with CyberEscudo's magic-bytes identifier. Educational content.