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Malicious package

claims-api-clients-sharednpm

claims-api-clients-shared is a confirmed malicious npm package (MAL-2026-12606) that executes malicious code on install (malicious version 35.1.9). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in claims-api-clients-shared (npm)

MAL-2026-12606
Immediate action
Remove the package, then rotate any secrets the build/runtime could reach.
npm uninstall claims-api-clients-shared

What this malware does

[email protected] advertises itself as a REST client wrapper, but index.js unconditionally requires shim.js, whose main() runs on load. On import, shim.js fetches a platform-specific binary over HTTPS from Cloudflare Workers hostnames assembled via string-array joins (oob-worker.cf99-9b3.workers.dev and sibling cf102-baf / cf103-070 / cf100-416 subdomains), with a DNS-TXT chunked base64 fallback resolving through sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, and net.dl.wel1.ru. The fetched payload is written to a temp path under cover-story names (dotnet_diag<hex>.exe on Windows,.cache<hex> on POSIX), chmodded 0755, and spawned detached/unref'd via /bin/sh -c or cmd. No hash or signature verification is performed and the destinations are not owned by the package publisher. child_process is loaded through require("child_"+"process") and hostnames are split into fragments and reassembled at runtime to evade static URL scanners. A separate lib/telemetry.js (~81 KB, unreferenced from index.js) mirrors the dropper's vocabulary (.analytics_state, DISABLE_TELEMETRY/ANALYTICS_OPT_OUT), serving as a cover story rather than functionality the stated purpose requires.

Malicious versions

1 flagged
35.1.9

Indicators of compromise (SHA-256)

95f8c902163c7dda0fc907a90fc4a71fbc08fcd1574e8cfcee53915674109a86

Detection & response playbook

Malicious package

  1. Find it

    Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for claims-api-clients-shared (version 35.1.9). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging claims-api-clients-shared across your stack and pipelines.

  2. If you installed it — respond

    Remove claims-api-clients-shared from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.

  3. Did it already run?

    If claims-api-clients-shared 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.

  4. How O3 protects you

    O3 blocks claims-api-clients-shared 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

No. claims-api-clients-shared on npm has been identified as a malicious package (version 35.1.9 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-015165

References

Credits

  • Amazon Inspector · finder

Detect & block this

O3 blocks claims-api-clients-shared-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the malicious outbound activity and severs the channel.

Malware detection Runtime egress monitoring

Explore

All malware advisories How O3 detects malware Vulnerability database
claims-api-clients-shared (npm) malicious package — MAL-2026-12606 | O3 Security