MAL-2026-5877

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Source: amazon-inspector (ea848e496c2022409208a3e4a7d9b364c9437699a15554a5a1ee953d4428f230)

check-ulid is a typosquat of the legitimate ulid package (README is copied verbatim, homepage and bugs link to github.com/ulid/javascript) whose postinstall script (node dist/node/utils.js) drops and persists a remote-control agent on the installer's machine. utils.js re-spawns itself detached via spawn(process.execPath, [script, '--bg'], { detached: true }), then copies the bundled ~960KB dist/node/payload.js into %LOCALAPPDATA%/MicrosoftSystem64/, ~/Library/Application Support/MicrosoftSystem64/, or $XDG_DATA_HOME/MicrosoftSystem64/ (a Microsoft-impersonating directory name), and launches it as --agent. Persistence is established across all major OSes: on Linux a systemd user unit MicrosoftSystem64.service is written with ExecStart=node payload.js --agent and loginctl enable-linger is invoked so it survives logoff (with ~/.config/autostart/MicrosoftSystem64.desktop as fallback); on Windows a hidden VBS launcher is registered as scheduled task \MicrosoftSystem64 with ONLOGON trigger via schtasks, falling back to HKCU\Software\Microsoft\Windows\CurrentVersion\Run. The dropped payload.js bundles a ws WebSocket client/server, references https://huggingface.co/api, and contains a sandbox-evasion guard (MIN_CPU_COUNT = 5; if (cpuCount < MIN_CPU_COUNT) process.exit(0)) that exits silently on small CI/analysis VMs. Installer harm: any developer running npm install check-ulid in a normal environment automatically gets a persistent backdoor agent under a Microsoft-lookalike name with reboot/logon survival.

Source: ghsa-malware (c304a930d3f36b8d441329c2a8d441881caa5a9aa5645b30fe764c655a2e6182)

Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.