Which versions of s3transfer-sl are malicious?

The following PyPI versions of s3transfer-sl are flagged malicious: 0.12.0, 0.12.1, 0.12.2, 0.12.3, 0.12.4, 0.12.5. Treat any of these as compromised.

How do I remediate s3transfer-sl if I installed it?

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.

I already installed s3transfer-sl — how do I know if it already compromised me?

If s3transfer-sl 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.

Is s3transfer-sl part of a known attack campaign?

Yes — s3transfer-sl is associated with the 2025-04-s3transfer-sl campaign. Packages in the same campaign often share infrastructure and payloads, so check whether any related packages are also in your dependency tree.

How do I find s3transfer-sl across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for s3transfer-sl (6 malicious versions).

Malicious package

s3transfer-slPyPI

Advisory published Apr 23, 2025Updated Dec 31, 2025

s3transfer-sl is a confirmed malicious PyPI package (MAL-2025-191861) that steals credentials and exfiltrates sensitive data (malicious versions 0.12.0, 0.12.1, 0.12.2…). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in s3transfer-sl (PyPI)

MAL-2025-191861

Immediate action

Remove the package, then rotate any secrets the build/runtime could reach.

pip uninstall s3transfer-sl

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):

exfiltration-cloud-tokens
clones-real-package
typosquatting

Malicious versions

6 flagged

0.12.00.12.10.12.20.12.30.12.40.12.5

Indicators of compromise (SHA-256)

5d10e122ebed25fab78cda8e7fd295eac6e3871a3017ccc1d8f0268c7d915569

e1cc7c88223c47e4c3ceecc6fe73d05c1cbb505061a009f8ae5caf37086a2e09

63ac1236be94096dd502d0448ce4360ead8b4d1d7bbe4091e71360b6b47d7f48

33513a3f1624f77353ee7b07dbfabcd90173e70d9a81b05972adebaf0f18132c

Detection & response playbook

Credential / info stealer

Find it
Search your lockfiles and build artifacts for s3transfer-sl (6 malicious versions).
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 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. s3transfer-sl on PyPI has been identified as a malicious package (versions 0.12.0, 0.12.1, 0.12.2, 0.12.3, 0.12.4, 0.12.5 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

2025-04-s3transfer-sl

References

bad-packages.kam193.eu

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.

Malware detection Runtime egress monitoring

Explore

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