Hash Extender is a command-line tool developed by Ron Bowes that implements length extension attacks against multiple hashing algorithms. The tool supports attacks against MD4, MD5, RIPEMD-160, SHA-0, SHA-1, SHA-256, SHA-512, and WHIRLPOOL hash functions. Length extension attacks exploit a vulnerability in certain hash functions where an attacker can append data to an original message and compute the hash of the extended message without knowing the original message content. Hash Extender simplifies the process of performing these cryptographic attacks by automating the complex mathematical operations required. The tool takes the original hash, known data, and additional data to append as inputs, then generates the extended hash and the complete message that would produce that hash. This functionality makes it useful for penetration testing scenarios where hash length extension vulnerabilities need to be identified and exploited in web applications or other systems that use vulnerable hash functions for authentication or integrity verification.