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Malicious package

claims-replace-url-paramsnpm

Advisory published Updated

claims-replace-url-params is a confirmed malicious npm package (MAL-2026-12641) that executes malicious code on install (malicious version 35.3.2). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in claims-replace-url-params (npm)

MAL-2026-12641
Immediate action
Remove the package, then rotate any secrets the build/runtime could reach.
npm uninstall claims-replace-url-params

What this malware does

The package's public API in index.js is a no-op class whose only real effect is require("./_adapter") on load. adapter.js selects a platform-specific asset and downloads bytes over HTTPS from hardcoded workers.dev hosts (oob-worker.cf101-adf.workers.dev) with a DNS-TXT fallback that assembles base64 chunks from *.dl.wel1.ru subdomains (sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, net.dl.wel1.ru). The fetched bytes are written to /var/tmp/.cache<hex> on Unix or %TEMP%\dotnet_diag_<hex>.exe on Windows, chmodded 0755, and spawned detached via /bin/sh -c or cmd.exe /c start. Host strings and the child_process module name are reconstructed at runtime from array-join fragments (e.g. ["oob-worker.cf","101-adf",".worke","rs.d","ev"].join(""), require("child_" + "process")) to defeat static string matching. lib/telemetry.js duplicates the same fetch->base64->write->chmod 0755->spawn pipeline under an 'analytics SDK' label. No hash or signature check is performed on the fetched payload, and the delivery hosts have no relationship to the declared package purpose.

Malicious versions

1 flagged
35.3.2

Indicators of compromise (SHA-256)

cfdefc5cd3c5418949e2da9656f7b93b174c5b8eb5fa64531736fbd5ae63b1f0

Detection & response playbook

Malicious package

  1. Find it

    Search your lockfiles and build artifacts for claims-replace-url-params (version 35.3.2).

  2. If you installed it — respond

    Remove claims-replace-url-params 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-replace-url-params was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.

Frequently asked questions

No. claims-replace-url-params on npm has been identified as a malicious package (version 35.3.2 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-015132

References

Credits

  • Amazon Inspector · finder

Detect & block this

O3 blocks claims-replace-url-params-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

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claims-replace-url-params (npm) malicious package — MAL-2026-12641 | O3 Security