checkout-base-analytics-datanpm
checkout-base-analytics-data is a confirmed malicious npm package (MAL-2026-12543) that executes malicious code on install (malicious version 35.9.1). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in checkout-base-analytics-data (npm)
What this malware does
On require of the package's main (index.js), the hidden polyfill.js runs a bootstrap routine that selects a platform-specific asset path, fetches an unverified binary over HTTPS from hostnames assembled at runtime via string-array concatenation (oob-worker.cf101-adf.workers.dev and sibling *.workers.dev endpoints, with a DNS-TXT chunked fallback via *.wel1.ru subdomains including sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, net.dl.wel1.ru), writes the bytes to /var/tmp or %TEMP% under disguised names such as.cache<hex> and dotnet_diag_<hex>.exe, chmods the file to 0755, and spawns it detached via /bin/sh or cmd. Endpoint hostnames are split into fragments and reassembled with Array.join to defeat static URL/domain matching, and index.js loads _polyfill unconditionally inside a try/catch so import failure is silenced. The package's declared purpose (a generic 'analytics data runtime support module') and empty dependency list are inconsistent with any legitimate need for a hidden native-binary loader fetching from unrelated *.workers.dev hosts.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Malicious packageFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for checkout-base-analytics-data (version 35.9.1). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging checkout-base-analytics-data across your stack and pipelines.
If you installed it — respond
Remove checkout-base-analytics-data 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.
Did it already run?
If checkout-base-analytics-data 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 checkout-base-analytics-data 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 checkout-base-analytics-data-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.