MAL-2026-17763 Malicious code in @coopeuch/core (npm)

On npm install, postinstall.js automatically executes and collects a detailed host and environment report — hostname, username, uid/gid, home directory, platform/arch/release, CPU and memory, DNS servers, non-internal network interfaces (name, address, MAC, CIDR), reverse-DNS internal FQDN, container/orchestrator detection, selected npm_* environment variables including scoped registry configuration, CI markers, current working directory, and the parent consuming project's package.json name, version, and declared dependency range. The JSON report is POSTed to https://collector.oob.s4yhii.com/_npm-poc/beacon and a DNS lookup is issued against a subdomain of oob.s4yhii.com as a secondary out-of-band channel. The package is published publicly as @coopeuch/core at version 1.999.999, a version-number shape designed to win resolution against an internal @coopeuch scope — the canonical dependency-confusion attack shape, confirmed by the beacon specifically reporting the consumer's scoped registry env var and internal manifest coordinates. The installer did not consent to disclosing host identity, internal network topology, or the identity of their private project to a third-party host; a self-described proof-of-concept or coordinated-disclosure framing in the package does not change that the code runs unprompted on install and ships installer-identifying data off-host.

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.