The npm package base65-15x is a malicious typosquat of the legitimate base-x package. Its decode() function does not perform base decoding but instead sends the input string to a hardcoded attacker-controlled server over plain HTTP and then throws an error. This behavior risks leaking sensitive data such as encoded keys, wallet addresses, and mnemonics to the attacker. The package version 5.0.2 is affected. Systems with this package installed should be considered fully compromised, and all secrets should be rotated immediately.