devplatform-react-query-s3-clientnpm
devplatform-react-query-s3-client is a confirmed malicious npm package (MAL-2026-12739) that steals credentials and exfiltrates sensitive data (malicious version 35.8.7). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in devplatform-react-query-s3-client (npm)
What this malware does
On require()/import of devplatform-react-query-s3-client, index.js loads vendor.js which selects a platform-specific payload path (linux_x64, linux_arm64, darwin, win32), fetches a binary from one of four Cloudflare Workers hosts whose names are assembled at runtime via array-join obfuscation (oob-worker.cf102-baf.workers.dev, oob-worker.cf103-070.workers.dev, oob-worker.cf99-9b3.workers.dev, oob-worker.cf100-416.workers.dev), with a DNS-TXT base64 fallback channel to sdk.dl.wel1.ru / ext.dl.wel1.ru / pkg.dl.wel1.ru / net.dl.wel1.ru. The downloaded bytes are written to /tmp or %TEMP% under a deceptive name (.cache<hex> or dotnet_diag_<hex>.exe impersonating.NET diagnostics), chmod 0755, and spawn-detached via /bin/sh -c '<path> &' or cmd.exe /c start. A second copy of the dropper (base64-chunk assembly, cp.spawn('/bin/sh', ['-c', filePath+' &']), fs.chmodSync(..., 0o755)) is duplicated in lib/telemetry.js under a ServiceDiscovery/WorkerHost class as an alternate loader. Opt-out env vars (DISABLE_TELEMETRY, ANALYTICS_OPT_OUT, DO_NOT_TRACK) and a /tmp/.analytics_state decoy provide a telemetry cover story; the destinations are hidden through string-split concatenation to defeat static grep. The payload is unpinned, unsigned, opaque, and delivered from hosts unrelated to any legitimate S3 or React Query SDK.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Credential / info stealerFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for devplatform-react-query-s3-client (version 35.8.7). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging devplatform-react-query-s3-client across your stack and pipelines.
If you installed it — respond
devplatform-react-query-s3-client is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.
Did it already run?
If devplatform-react-query-s3-client 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 devplatform-react-query-s3-client 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 devplatform-react-query-s3-client-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.