XlsGen is a proof-of-concept tool designed to generate Excel BIFF8 files with embedded 4.0 macros without requiring Microsoft Excel to be installed. The tool enables programmatic creation of xls files that contain macro functionality, bypassing the need for the actual Excel application during file generation. This capability allows security researchers and penetration testers to create Excel files with embedded macros for testing purposes, social engineering simulations, or malware analysis scenarios. The tool operates by directly manipulating the BIFF8 file format structure to embed macro code into the generated Excel files, providing a method to create macro-enabled spreadsheets through code rather than through the Excel interface.