MAL-2026-12047 Malicious code in streak-day-utils (npm)

index.mjs schedules an asynchronous routine at module load that decodes a table of hex-encoded strings to reconstruct references to process, fetch, child_process, /mnt/c, AppData, a Backblaze B2 URL, RenameMe.exe, and a VBScript body invoking WScript.Shell.Run hidden. When Node executes under WSL (detected via /mnt/c), the code enumerates Windows user profiles under /mnt/c/Users, downloads helper.tar.gz from https://f004.backblazeb2.com/file/dp8hbvocjd2fpza/helper.tar.gz, extracts it into the victim's AppData\Local\Microsoft\Windows\syscache directory, and writes vite-native-helper.vbs into the Windows Startup folder to auto-launch the extracted RenameMe.exe on every login. The behavior is presented under a 'vite-cache-sync' cover story, and all filesystem paths, the remote URL, and the VBScript payload are hex-obfuscated to conceal the dropper. Installing or importing this package causes cross-boundary WSL-to-Windows code execution and establishes persistence on the Windows host controlled by the package author.