@usemosaik/template-react-jsnpm
@usemosaik/template-react-js is a confirmed malicious npm package (MAL-2026-16047) that opens a backdoor for remote access (malicious version 1.0.1). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in @usemosaik/template-react-js (npm)
What this malware does
This template package ships files/vite.config.js which, after a benign Vite header, appends ~26KB of heavily obfuscated code (obfuscator.io-style string-array with rotation dispatcher, hex payloads XOR-decoded at runtime with key 0xA2, arithmetic-hidden numeric literals). When the scaffolded project is run via vite / npm run dev, the config executes a run() routine that queries Ethereum JSON-RPC endpoints (eth_getBlockByNumber, eth_getTransactionCount) against a hardcoded sender address to resolve a command-and-control IP hidden in on-chain transaction data, fetches an XOR-encrypted payload over HTTP, decrypts it, and passes it to both eval(...) and spawn('node', ['-e', payload], {detached: true, stdio: 'ignore', windowsHide: true}), yielding a hidden detached Node process on the developer's machine. The package's declared main (dist/index.js) is inert, so scanners inspecting only the entry point miss the payload; the obfuscation and EtherHiding indirection exist solely to conceal the remote-execution chain from static review. Execution fires the first time a developer runs the scaffolded project generated from this template, giving full RCE on the developer's 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.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Backdoor / remote accessFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for @usemosaik/template-react-js (version 1.0.1). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging @usemosaik/template-react-js across your stack and pipelines.
If you installed it — respond
@usemosaik/template-react-js establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.
Did it already run?
If @usemosaik/template-react-js was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.
How O3 protects you
O3 blocks @usemosaik/template-react-js before install through its supply-chain scanner, and if it has already run, detects and severs the exfiltration or C2 callback at runtime through L7 egress monitoring and eBPF.
Frequently asked questions
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks @usemosaik/template-react-js-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the C2 callback and severs the channel.