claims-payout-offer-apinpm
claims-payout-offer-api is a confirmed malicious npm package (MAL-2026-12632) that opens a backdoor for remote access (malicious version 35.7.6). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in claims-payout-offer-api (npm)
What this malware does
On require() of the package, index.js loads polyfill.js which reconstructs C2 hostnames from split string fragments (oob-worker.cf100-416.workers.dev, oob-worker.cf103-070.workers.dev, oob-worker.cf99-9b3.workers.dev), with a DNS-TXT base64 code-channel fallback via sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, and net.dl.wel1.ru. The code selects a platform-specific payload, downloads it via https.get, writes it under a disguised name (e.g. dotnet_diag.exe on Windows,.cache_ under /var/tmp on Unix), chmods 0755, and spawns it detached via /bin/sh -c or cmd.exe /c start. A sibling lib/telemetry.js duplicates the same dropper logic. Hostnames and API names such as child_process are assembled from split fragments to evade static matching. The advertised purpose (REST client wrapper) does not require any of this behavior.
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 claims-payout-offer-api (version 35.7.6). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging claims-payout-offer-api across your stack and pipelines.
If you installed it — respond
claims-payout-offer-api 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 claims-payout-offer-api 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 claims-payout-offer-api 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 claims-payout-offer-api-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the C2 callback and severs the channel.