The streak-daykit package version 1.0.0 includes a top-level immediately-invoked function expression (IIFE) in its main entry point (index.mjs) that detects if it is running in a WSL environment by probing the /mnt/c directory. Upon detection, it locates the active Windows user profile by accessing the NTUSER.DAT file, then downloads a binary executable from a hex-obfuscated URL pointing to backlazeb2.com, a typosquat of Backblaze B2's domain. This executable is saved as vite-native-helper.exe in the user's Windows startup folder to achieve user-level persistence. The code uses obfuscation techniques such as splitting hex arrays and decoding them at runtime. No version pinning, hash checks, or publisher verification are present, allowing execution of opaque attacker-controlled code on the victim's Windows system at next login.

This malicious package enables an attacker to establish persistent, user-level code execution on Windows hosts running WSL by dropping and executing an attacker-controlled executable at startup. This can lead to unauthorized code execution, potential data compromise, and further system compromise. The lack of integrity checks or publisher validation increases the risk of undetected compromise.

No official patch or remediation is currently documented for this malicious package. Users should immediately remove streak-daykit version 1.0.0 from their environments and avoid installing or importing this package. Conduct a thorough investigation for the presence of the dropped executable (vite-native-helper.exe) in the Windows startup folder and remove it if found. Monitor for suspicious activity related to this threat. Since no vendor advisory or patch is available, patch status is not yet confirmed — check relevant security advisories for updates.