s3transfer-slPyPI
Malicious code in s3transfer-sl (PyPI) Remove it immediately and rotate any exposed credentials.
What this malware does
During installation, the package attempts to exfiltrate env variables and tokens from Azure metadata API. It's a malicious clon of s3transfer
Category: MALICIOUS - The campaign has clearly malicious intent, like infostealers.
Campaign: 2025-04-s3transfer-sl
Reasons (based on the campaign):
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exfiltration-cloud-tokens
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clones-real-package
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typosquatting
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 s3transfer-sl (6 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging s3transfer-sl across your stack and pipelines.
If you installed it — respond
s3transfer-sl 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 s3transfer-sl 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 s3transfer-sl 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
- Kamil Mańkowski (kam193)
Detect & block this
O3 blocks s3transfer-sl-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.